The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino oscillation experiment. DUNE’s main goal is to provide unprecedented sensitivity in the search for neutrino CP violation, to determine the neutrino mass hierarchy, and to make precision measurements of neutrino mixing parameters. DUNE will be sensitive to low-energy neutrinos coming from supernova bursts, bringing insight for both particle physicists and cosmologists. DUNE’s ambitious physics program also includes searches for proton decay and non-standard neutrino interactions. The experiment will utilize a new broadband high-intensity neutrino beam and a suite of Near Detectors at Fermilab, along with Far Detectors situated 1300 km from Fermilab at the Sanford Underground Research Facility.
This presentation reviews DUNE’s extensive physics program and experimental design, as well as recent progress. The ongoing and future activities of the recent Canadian effort will be presented, with an emphasis on how researchers and students can contribute.

New results from the ATLAS Collaboration finds evidence for the production of four top quarks in the LHC collisions, providing a unique opportunity to study the top quark’s relationship to the Higgs boson. The rate of this process could be affected by various new theories that go beyond the Standard Model, providing an exciting window to search for new physics. This talk summarizes the results using proton-proton collision data at a centre of-mass energy of 13 TeV with leptonic final states. Machine learning techniques are used to better discriminate the signal events from the overwhelming background. The observed signal significance is 4.7 standard deviations above the background and is consistent with the Standard Model expectation within 2.0 standard deviations. 

The planned upgrade of the LHC to its high luminosity version (HL-LHC) around 2027 will bring about a drastic increase in instantaneous luminosity and simultaneous interactions per bunch crossing. Currently, most LHC experiments use Kalman Filter-based track reconstruction algorithms which exhibit outstanding physics performance but scale poorly with the amount of data produced in each bunch crossing. Therefore, the high energy physics community is currently performing intensive R\&D to commission new and/or improved algorithms for this crucial data reconstruction task. During this seminar, I will present many different approaches ranging from running existing algorithms on accelerated hardware to complete end-to-end neural network track reconstruction pipelines. A new algorithmic testbed for research in track reconstruction, ACTS, will also be discussed.

The cosmological constant and the discrepancy between its observed value and its theoretical estimate may be the worst prediction in the history of physics. In this talk, I will present a scalar-tensor scenario that can dynamically damp the cosmological constant and provide a viable solution to this fine-tuning problem. I will show that the effect of this model on the cosmological evolution is indistinguishable from the one predicted by general relativity and satisfies the fifth force constraint.

L’histoire des neutrinos débute en 1930, lorsque Pauli a proposé une nouvelle particule pour expliquer le spectre continu d’énergie de l’électron émis dans une désintégration bêta. Cette particule, qu’on a appelé le neutrino, devait être non-chargée, très pénétrante et de spin 1/2. Le Modèle Standard de la physique des particules (MS) contient trois saveurs de neutrino. L’oscillation des neutrinos est un phénomène qui fait passer un neutrino d’une saveur à une autre saveur au cours de la propagation du neutrino. Une conséquence de l’observation des oscillations des neutrinos, qui a mérité le prix Nobel en 2015, est que leur masse doit être non-nulle. L’origine de cette masse est un mystère: le MS ne fournit pas d’explication. Il y a deux possibilités théoriques : une masse de Dirac ou une masse de Majorana. Si le neutrino est de type Majorana (ce qui signifie que l’antiparticules et la particule sont en fait la même particule), on devrait observer des processus qui ne conservent pas le nombre leptonique. Un exemple est la double désintégration bêta sans émission de neutrinos (0νββ). 

Il y a des processus similaires à 0νββ qui brisent de la conservation du nombre leptonique, à basse énergie, mais il est aussi possible de le produire à haute énergie, au collisionneur LHC. Si on observe ce processus au Large Hadronic Collider (LHC) au CERN, il y a aussi la possibilité de chercher la violation CP. Il y a des processus similaires à 0νββ qui brisent la conservation du nombre leptonique, à basse énergie, mais il est aussi possible de le produire à haute énergie, au collisionneur LHC. Étude de la violation CP nous donnerait des informations sur de la Nouvelle Physique qui ne pourraient pas être facilement obtenues autrement.

The near-field approximation of General Relativity is an unfamiliar subject with a lot of interesting topics. Here we'll talk about the absence of aberration (i.e. : the fact that the gravitational force is directed to the instantaneous position of any object moving uniformly).  This should happen in order to reproduce the Newtonian force even if, the speed of gravity being finite, one could think the direction of the force should be pointing to the retarded position.

Then we will discuss the value of the fields in the near-field zone, highlighting the absence of dipole effects and how this is related to the conservation of energy-momentum.

Astrophysical and cosmological observations support that dark matter constitutes more than 80$\%$ of the matter in the universe. Understanding the nature of DM will make possible to reconstruct the early universe history since all the experimental data that we have related to universe evolution comes from BBN era onwards.
The current Standard Model of particle physics is not able to explain the nature of DM therefore extensions seem necessary to account for new particles that predict be viable dark matter candidates.  Currently the QCD axion is an attractive candidate to explain the origin of DM, although axions are extremely light, there are mechanisms corresponding to non-thermal production of axions able to produce axion dark matter in the early universe in such a way that it accounts the total dark matter density currently measured ($\Omega_{cdm}=0.26$).
A mechanism corresponds to misalignment mechanism, which consists in the fact that after the PQ phase transition the axion evolves like a massless scalar field, but close to the QCD era ($\Lambda_{QCD}$,the axion acquires an effective  potential due to instanton effects. The equation of motion for the field corresponds to

 \begin{equation}
     \dot \theta+ 3\,H(t)\theta+ m_a^2(t)\,sin\theta=0, 
 \end{equation}

At high temperatures ($T>>\Lambda_{QCD}$), the field is stuck on a constant value, corresponding to the initial misalignment angle of the axion . But, when expansion rate H(t) becomes comparable to the axion mass, the axion field begins to oscillate around the minimum and coherent oscillations are generated, which behave like cold dark matter,  i.e. their energy density evolves as $\rho\sim R^{-3}$.
The standard cosmology establishes that before Big Bang Nucleosynthesis (BBN) there was a radiation-dominated era, where its expansion rate of the universe generates a parameters space where axion QCD could be dark matter.
In this work, we assume the scenario of a new period before BBN where extra field $\phi$ present at the early universes (After Inflation) and that eventually, due to its equation of state,$P_\phi=\omega \rho_\phi$, dominates the energy density of the universe.  Prior to BBN the field decays with a decay rate $\Gamma_\phi$ and the universe is radiation dominated as hinted by observations.
Finally, we have different compatible cosmologies with the axion being the total CDM content of the universe, providing in a window for axion parameters according to the cosmology used.
 

VERITAS is a gamma-ray observatory composed of an array of four 12-m imaging atmospheric Cherenkov telescopes, located in Arizona. VERITAS is sensitive to gamma rays in the very-high-energy (VHE, E > 100 GeV) range, where the sky is dominated by non-thermal emission from extreme environments and extreme astrophysical objects. VERITAS has an extensive science program dedicated to the study of active galactic nuclei and the observation of Galactic sources such as supernova remnants, pulsar wind nebulae, and gamma-ray binaries, among other sources. VERITAS observations have also enabled searches for dark matter, provided insights into the properties of cosmological radiation fields, and allowed multi-messenger searches for high-energy neutrino and gravitational wave emitters. In addition, benefitting from the large optical aperture of its telescopes, VERITAS has developed a program of optical observations which is already delivering significant results.

This talk will present some highlights from VERITAS observations of the high-energy universe. 

I will discuss the possibility that neutrons decay in a nonstandard way, perhaps into the dark matter of the Universe. This has profound implications for neutron stars which rules out the simplest scenarios. I will describe ways to avoid this exclusion and how they will be tested.

The fundamental physical description of Nature is based on two mutually incompatible theories: Quantum Mechanics and General Relativity. Their unification into a theory of Quantum Gravity (QG) remains one of the main challenges of theoretical physics. A common feature of candidate theories of QG is the existence of a minimal observable length of the order of the Planck length. This prediction, though, is in contradiction with Heisenberg’s Uncertainty Principle. In fact, according to this principle it is possible to observe any length while increasing the uncertainty in momentum. In the context of Quantum Gravity Phenomenology, that studies QG effects in low-energy systems, Heisenberg’s principle is then modified into the Generalized Uncertainty Principle (GUP). GUP then imposes a minimal uncertainty in position and predicts a deformed commutation relation between position and momentum. In this talk, after introducing the basics of the Uncertainty Principle, I will show how the GUP can change known aspects of standard Quantum Mechanics, leading to ways to test theories of QG.

We introduce two new effective quantities for the study of comoving curvature perturbations ζ: the space dependent effective sound speed (SESS) and the momentum dependent effective sound speed (MESS) . We use the SESS and the MESS to derive a new set of equations which can be applied to any system described by an effective stress-energy-momentum tensor (EST), including multi-fields systems, supergravity and modified gravity theories. We show that this approach is completely equivalent to the standard one and it has the advantage of requiring to solve only one differential equation for ζ instead of a system, without the need of explicitly computing the evolution of entropy perturbations. The equations are valid for perturbations respect to any arbitrary flat spatially homogeneous background, including any inflationary and bounce model. 
As an application we derive the equation for ζ for multi-fields KGB models and show that observed features of the primordial curvature perturbation spectrum are compatible with the effects of an appropriate local variation of the MESS in momentum space. The MESS is the natural quantity to parametrize in a model independent way the effects produced on curvature perturbations by multi-fields systems, particle production and modified gravity theories and could be conveniently used in the analysis of LSS observations, such as the ones from the upcoming EUCLID mission or CMB radiation measurements

The Cosmic Microwave Background data confirm several aspects of inflationary universe scenario very well. In particular scale invariant perturbations are successfully generated. A few data points remain off the fitted curve and we seek a physical origin for them. It is shown that several desirable quantitative elements of inflationary model are constrained much better if the features are of physical origin. The features are obtained in a model independent way first. We then consider possible sources for such features at the earliest phase of inflation which lies well within the grand unification era. An SO(10) model can in principle have the desirable features in the form of topological pseudo-defects.

After explaining the spirit behind the so called low energy theorems, LETs (more accurately, low momentum transfer theorems), I will first demonstrate their great powers in delivering many important results in particle physics. I will then show how Francis Low applied this to electromagnetic radiation. After describing some of Weinberg’s pioneering works in applications to gravitation, I will describe my own work on gravitational radiation using LET’s, reproducing Einstein’s quadrupole formula. I shall bring out various nuances and discuss future prospects. 

One of the most prominent questions in the fields of particle physics and cosmology is the nature of dark matter which comprises 85% of the total mass of the universe. The PICASSO and PICO experiments are both direct detection experiments situated at SNOLAB that use the superheated liquid or bubble chamber technique to search for dark matter. The PICASSO collaboration pioneered the use of this technique for dark matter searches, and moreover, discovered an important background suppression feature: the acoustic alpha-neutron discrimination. The last PICASSO result was published in 2017 and still holds to this day the best spin-dependent limit for weakly interacting dark matter candidates (WIMPs) with a mass of 4 GeV. Since the merger of the PICASSO and COUPP, PICO holds the world best spin-dependent WIMP cross sections limit set by the recent PICO60 detector result. PICO is currently building a new detector called PICO40L with a significantly improved design which will allow to substantially decrease the neutron background by a factor of ~50 and pave the way forward for the next stage, PICO500, which will contain approximately 500L of superheated liquid.

De nos jours, l'une des questions fondamentales en physique des particules est la nature de la matière sombre. Les expériences PICASSO et PICO sont deux expériences de détection directe qui sont situées à SNOLAB et qui utilisent des chambres à bulles remplies de fréons surchauffés. La collaboration PICASSO a été la première expérience à utiliser des chambres à bulles dans le but spécifique de découvrir la matière sombre et a de plus découvert l'existence de la discrimination acoustique entre les neutrons et les particules alpha. Le dernier résultat de l'expérience PICASSO a été publié en 2017 et possède, jusqu'à ce jour, la meilleure limite sur la section efficace d'interaction entre la matière sombre et la matière baryonique qui dépend du spin pour des masses de WIMP inférieures à 4 GeV. Depuis la fusion des collaborations PICASSO et PICO, l'expérience PICO détient la meilleure limite au monde pour toute autre masse de WIMP. Actuellement, la collaboration PICO est en train de construire le détecteur PICO40L dont le bruit de fond dû aux neutrons sera radicalement diminué par un facteur ~50 et qui sert de prototype pour l'amélioration du design du prochain détecteur, PICO500, qui contiendra environ 500L de fréon.

Cosmic Rays have remained an enigma for over a hundred years since their discovery. This talk focuses on a well-measured, yet similarly elusive feature; an unexplained structure in arrival direction spanning many energies and angular scales. We now introduce a new way of exploring Cosmic Ray Anisotropy: observation through secondary neutrinos. Studying the cosmic rays' neutral daughter particles with pointing capabilities, like neutrinos, could shed new light. This can be done at two levels; a source, which produces cosmic rays, must also produce high energy astrophysical neutrinos, and low energy atmospheric neutrinos are made when the cosmic rays interact with the atmosphere. This analysis focuses on atmospheric neutrinos detected by IceCube, a Cherenkov detector instrumenting a kilometer cubed of glacial ice at the South Pole. IceCube has studied the anisotropy and its energy dependence in the Southern sky using atmospheric muons.

Using IceCube and a high-acceptance dataset of atmospheric neutrinos created for this analysis, we are nearing the sensitivity threshold to observe the phenomenon in atmospheric neutrinos arriving from the Northern Hemisphere. This analysis focuses on energy ranges that correspond to the spatially-consistent lower energy features of the dipole structure. Due to the statistical limitations of the neutrino dataset in comparison to the cosmic ray datasets, we also introduce new methods for detecting signal along with the standard multipole analysis methods. These include a 1D relative intensity fit to determine the amplitude and phase of the dipole, and a 2D binned log-likelihood analysis focusing on searching for observed anisotropy maps from the Tibet collaboration. Future hope for the work is to create a single-detector all-sky map of the anisotropy, minimizing systematical difficulties combining datasets from separate collaborations.

Supersymmetry (SUSY) is an attractive framework to extend the Standard Model since it solves several of its shortcomings simultaneously. This includes the hierachy problem if the mass of some of the superpartners are especially light. For SUSY models to be natural, i.e. to fix the hierachy problem with acceptably moderate fine tuning, the mass of the superpartners of the Higgs field (higgsino), top and bottom quarks (stop and sbottom) and of the gluon field (gluino) are particularly constrained. These superpartners are thus a good bet to be discovered first at the Large Hadron Collider (LHC). I will present the status of their searches at the ATLAS experiment.

The top quark is the heaviest elementary particle ever discovered. As such it holds a special relationship with the recently-discovered Higgs boson and could be central to searches for physics beyond the Standard Model. I will highlight some of these measurements and describe in more details ATLAS measurements of differential top quark pair production cross-section as well as a novel analysis looking for CP-violation in b-hadron decays using top quark events.

For the last few decades, High Energy Physics has been a victim of its own early success. Despite numerous theoretical arguments why it cannot be the final explanation for the interactions of fundamental particles, the Standard Model of particle physics continues to withstand intense scrutiny of the most determined experimental physicists. One promising way to search for signs of new physics is at the energy frontier at the LHC, probing energies comparable to those present very shortly after the Big Bang.

In this talk, I will review some recent experimental results for searches for new physics using data from the ATLAS experiment. Signs of new physics could also first show up as subtle surprises in the behaviour of the known particles, which could indirectly hint at new physics. I will discuss details about the detector performance, with a focus on the ATLAS inner tracker, which are crucial for such searches and precision measurements in particular, and highlight the potential of the future phase-II upgrade of the ATLAS inner tracker. I will conclude with a discussion on recent results on dark matter and new physics with GAMBIT, the Global and Modular Beyond-the-Standard Inference Tool, including first results of recasting early LHC Run-2 electroweak SUSY searches.

Starting in 2021, the Large Hadron Collider (LHC) will increase its operational energy, luminosity and number of interactions per collision. These conditions result in a factor of 10 more physics events, and up to 25% more overlapping processes in each event. This environment will make it difficult for the ATLAS trigger system to efficiently decide which data to store. This talk describes how a new hardware system, called the ATLAS Fast TracKer (FTK), will allow ATLAS to keep up with the demanding LHC conditions. Analyses that benefit from the FTK’s potential to improve b-quark and tau-lepton identification are discussed. These analyses have the potential to shed light on B-anomalies and gravity’s role in the Standard Model.

Readout upgrades that are aimed at improving electron and muon measurements are briefly discussed. Analyses that could benefit electron, muon, b-quark and tau identification include searches that address how neutrino masses and dark matter fit into the Standard Model.

Two outstanding questions in physics are the nature of dark matter and the origin of the matter- antimatter asymmetry in the universe. Astrophysical observations imply the existence of dark matter, an invisible and dominant mass component in the universe, but it has eluded direct detection to date. A measurement of charge-parity (CP) violation in the lepton sector may help explain the observed preponderance of matter over antimatter. I will present new results from the XENON1T dark matter search experiment, consisting of a multi-tonne dual-phase (liquid-gas) xenon time projection chamber, as well as my future plans for the measurement of CP violation by the T2K long-baseline neutrino oscillation experiment and the next-generation large water Cherenkov detector, Hyper-Kamiokande, attempting to answer these two questions.

Seminar on Thursday, March 22, 13:30, Flavorful Higgs bosons
Measurements of Higgs production and decays have revealed that most of the mass of the weak gauge bosons is due to the 125 GeV Higgs. Similarly, we know that the Higgs is at least partially responsible for giving mass to the top and bottom quarks and the tau lepton. Much less is known about the origin of mass for the first two generations. In this talk, I will discuss a framework in which the first and second generation masses originate from a second source of electroweak symmetry breaking and outline the phenomenological implications.

Note: colloquium on Friday, March 23, 11:30 in G-715:  Hints for flavorful new physics

I will survey the status of Deep Learning in High Energy Physics, with focus on new emerging techniques. I will discuss the path from the current state of mostly proof of principle and feasibility studies to physics results incorporating the new techniques and eventually incorporating Deep Learning into the production workflow of HEP experiments. And I will propose future Deep Learning projects in HEP.

One of the important tests of the SM is the measurement of the top quark Yukawa coupling, directly measured via the associated production process pp → tt̄H. The fourfold increase of the tt̄H cross section from √s = 8 to 13 TeV and the high statistics of top quark sample collected by the LHC experiments allow to increase the sensitivity of the search of this process. Both ATLAS and CMS have performed searches of tt̄H targeting the most relevant Higgs decays modes in final states with multileptons, high b-jet multiplicity or containing two photons, at √s=13 TeV. In this talk, the latest results on the search for the tt̄H process with the ATLAS experiment will be discussed, together with a comparison to the CMS performance and an outlook of these measurements with higher statistics.

The Standard Model (SM) of particle physics, despite its impressive ability to describe the phenomenology of fundamental interactions up to energy scales of several TeV, is believed to be incomplete; this becomes manifest at much higher energies and prevents a better understanding of cosmological features (dark matter, spacetime singularities such as black holes or the Big Bang...). Supersymmetry is a mature theoretical framework proposed to extend the SM's range of validity and pave the way to a quantum description of gravity. It predicts the existence of new heavy partners of the SM elementary particles, which may be produced in the LHC proton-proton collisions and result in rich and distinctive experimental signatures. Consequently, the ATLAS and CMS collaborations have made substantial efforts to search for evidence of these "superpartners".
After briefly introducing Supersymmetry, its motivations and its predicted phenomenology, I will present an overview of the latest searches for the superpartners of gluons and light quarks, highlighting the experimental methods that have been developed to enhance the sensitivity to those signals.

For some time now, there have been some disagreements with the standard model in the B->Kpi decays. In this talk, I will look at the consequences of the latest data on this "B->Kpi puzzle", and if a solution can be found in new physics models involving Z' and diquarks.

Despite the best efforts of many people, physics beyond the standard model has yet to be discovered. A variety of exotic signatures that would hide from traditional searches have been postulated in an attempt to explain where such new physics could be hiding. This seminar will provide an overview of some of the stranger, more exotic models that are searched for at LHC experiments, with an emphasis on long-lived, neutral particles.

Rather than focus only on the analysis I've worked on, I thought it would be nice to provide a full overview of all the more obscure signatures searched for.

Einstein’s celebrated quadrupole formula lies at the foundation of the first indirect evidence for gravitational waves: it explains with high precision the shrinking of the orbital radius of the Hulse-Taylor system. The formula expresses the power radiated in the form of gravitational radiation in terms of the source quadrupole moments. However, the derivation assumes a flat spacetime background, but there is strong observational evidence for a positive cosmological constant. To account for this, the quadrupole formula is generalized by replacing the flat spacetime background with a de Sitter spacetime. In this talk, I will focus on the conceptual subtleties that arise and comment on physical implications.

La conférence du International Committee for Future Accelerators (ICFA) s’est tenue du 6 au 9 novembre à Ottawa. ICFA est l'organisme qui représente les intérêts de la physique des particules dans le monde. Cette conférence avait pour but de faire le point sur l’état de la physique des particules, et de discuter des infrastructures nécessaires à l’avancée de cette science dans le futur. Je ferai un résumé de cette conférence. Étant limité dans le temps, je vais mettre l’emphase sur les futures expériences de collisionneurs à haute énergie, tels que le International Linear Collider au Japon et le Future Circular Collider au CERN. Dans le domaine du possible je parlerai aussi de matière sombre, neutrinos et de physique de la saveur.

Searching for the production of Higgs boson in association with a pair of top quarks would allow a direct measurement of the top quark Yukawa coupling and will provide an important test of the Higgs mechanism within the Standard Model. A search for this process is presented using proton- proton collisions at sqrt(s) = 13 TeV, collected by the ATLAS detector in both 2015 and 2016. Higgs boson decaying to two b quarks, and top pair decaying in semi-leptonic or dileptonic are considered.

Hidden sector or dark sector states appear in many extensions to the Standard Model, to provide a candidate for the darkmatter in the universe or to explain astrophysical observations of positron excesses. A hidden or dark sector can be introduced with an additional U(1)_d dark gauge symmetry. The presence of the dark sector could be inferred either from deviations from the SM-predicted rates of Drell-Yan (DY) events or from Higgs boson decays through exotic intermediate states. The discovery of the Higgs boson during Run 1 of the Large Hadron Collider opens a new and rich experimental program that includes the search for exotic decays H —> Z Zdark —> 4l and H —> Zdark Zdark —> 4l, where Zdark is a dark vector boson.

Les neutrinos semblent détenir de l'information clé sur notre Univers et nous sommes maintenant équipés pour les étudier en détail. Comprendre les neutrinos pourrait nous indiquer pourquoi l'Univers est dominé par la matière, pourquoi les neutrinos ont une si petite masse et s'il existe de nouveaux types de neutrinos. Cependant, étudier les neutrinos n'est pas une tâche facile. Les neutrinos ont démontré que leurs interactions sont beaucoup plus complexes que le nous croyions et leur faible interaction demande de très larges détecteurs. Les développements récents de la technologie de détecteurs à argon liquide apportent des opportunités uniques pour étudier ces mystérieuses particules avec une précision inégalée. Après avoir revu les questions d'intérêts en physique des neutrinos, je décrirai les détecteurs à argon liquide et comment ils peuvent nous aider à répondre à ces questions. Je terminerai par un survol des expériences, actuelles et futures, qui utilisent cette technologie.

The Skyrme model is a model for nuclear physics that describes atomic nuclei as topological soliton solutions, called skyrmions, in an effective field theory of pions. We study radial vibrations of spherically symmetric skyrmions in the Skyrme model and its variants. Concretely, we numerically solve the linearised field equations for small fluctuations in a skyrmion background, both for linearly stable oscillations and for (unstable) resonances. This is complemented by numerical solutions of the full nonlinear system, which confirm all the results of the linear analysis. In all cases, the resulting fundamental excitation provides a rather accurate value for the Roper resonance, supporting the hypothesis that the Skyrme model already gives a reasonable approximate description of this resonance.

Les observations astronomiques et cosmologiques prédisent l'existence de la matière sombre,
et qu'elle constituerait 85% de la masse totale de l'univers.

Le projet PICASSO a été mis sur pied afin de détecter directement les reculs nucléaires causés
par la collision entre un neutralino et un atome de fluor du fréon qui compose la masse active des détecteurs à gouttelettes surchauffées. Le fréon de C₄F₁₀ étant maintenu dans un état liquide métastable, le dépôt d'énergie occasionné par un recul nucléaire provoque une transition de phase de l'état liquide à gazeux et génère à travers le détecteur une onde de pression qui peut être enregistrée par des senseurs piézo-électriques.

L'étalonnage des détecteurs à gouttelettes surchauffées avec des neutrons est nécessaire afin de pouvoir comprendre leur fonctionnement et pour prédire leur réponse aux neutralinos. Cela est fait avec l'accélérateur Tandem de l'Université de Montréal.

Les mesures prises avec l'accélérateur sont ensuite comparées à des simulations Monte Carlo réalisées avec GEANT4 qui reproduisent entièrement l'expérience d'étalonnage, de la géométrie du montage jusqu'à l'énergie déposée lors des interactions nucléaires.

Les résultats de l'étalonnage permettent finalement d'obtenir de meilleures limites d'exclusion sur la section efficace dépendante du spin de l'interaction entre le neutralino et le proton qui sont extraites des données expérimentales acquises au laboratoire souterrain SNOLAB.

The di-Higgs production is an important channel for more direct determination of the Higgs self couplings. We focus on the situation that the production is amplified where the observed Higgs doublet couples with a singlet scalar. The singlet can interact with gluon strongly by the mediation of new colored particles. Here, constraints from the 125 GeV Higgs signal strengths do not restrict the scenario severely. We can probe such a situation by observation of the resonant production of a new singlet-like scalar through the di-Higgs channel. We also address a possible explanation for the 2.4 σ excess in the search for Higgs pair production with the bbγγ final state at the ATLAS experiment.

This talk is based on the ongoing collaboration with Koji Nakamura (KEK & ! CE RN), Kin-ya Oda (Osaka Univ.), Seong Chan Park and Yasuhiro Yamamoto (Yonsei Univ.).

Nuclear Track Detectors (NTD) have been used in the detection of heavy charged particles for many years. Their main advantage, apart from low cost and ease of use, is the existence of natural thresholds of registration, which provide a natural and easy way of suppressing the background in an experiment looking for rare events (e.g. Strangelets, Monopoles) in cosmic rays and particle accelerators. In this presentation, I will talk about how an inexpensive, commercially available plastic called Polyethylene Terephthalate (PET), commonly used as a packaging and bottling material, was found to be suitable as a NTD with a threshold much higher than many other materials commonly used as NTDs and the use of PET in the search for strangelets in cosmic rays. In addition, I will describe how NTDs are being used in the search for monopoles at LHC.

The​ concept of topology in condensed matter physics ​has ​won the 2016 noble prize​ in physics​.​ Usually, topological band theory is attributed to electronic systems only. ​  Recently, researchers have extended ​the concept of topological condensed matter​  to non-electronic systems such as spin waves  in quantum magnets​ (magnon)​ and mechanical waves​ ​in solids​ (phonon)​. In this talk, I will give a general exposition of topological magnon insulators and magnon Hall effect in quantum magnetic systems, in which the Dzyaloshinskii-Moriya interaction (DMI) is the driving force similar to  spin-orbit coupling (SOC) in electronic systems.  I will also discuss recent experimental realizations of this phenomenon. In the last part of the talk, I will show that the DMI​ or SOC​ is not the primary​ source​ of topological spin excitations in magnetic systems with spin frustrations. ​This interaction can be zero and topological spin excitation still persists. This is in sharp contrast to previous ​experimental reports in ​insulating ​ferromagnet​s​​  Lu2V2O7 and Cu(1-3, bdc).

A century of research on cosmic rays has revealed many of the fundamental properties of these energetic particles, such as their chemical composition and energy spectrum. The sources of cosmic rays, however, remain unknown. The discovery of a flux of high-energy astrophysical neutrinos by the IceCube observatory in 2013 may hold the key to solving this enduring question. High-energy neutrinos, as well as gamma rays, are produced in hadronic cosmic-ray interactions occurring at their source or during propagation. While no neutrino source has been identified so far, the sensitivity of these studies can be increased by searching for gamma-ray counterparts in temporal and spatial correlation with the IceCube neutrino events. The detection of gamma-ray emission in coincidence with an astrophysical neutrino would represent a smoking-gun signature of a cosmic-ray production site and potentially reveal details about the acceleration medium. In this talk I will present the status and recent results from the neutrino follow-up program of the VERITAS observatory, an air-Cherenkov telescope array in southern Arizona USA dedicated to gamma-ray astronomy in the very-high-energy range (VHE, E > 100 GeV). I will also describe prospects for neutrino follow-up observations using the Cherenkov Telescope Array, a next-generation VHE gamma-ray instrument. 

Abstract: Astronomical and cosmological observations strongly suggest the presence of dark matter. The direct search for evidence of Weakly Interacting Massive Particle (WIMP) dark matter continues to be one of the forefront activities in experimental particle physics. In this talk I will give an overview of the evidences of dark matter and present in particular XENON1T experiment which has achieved world-leading sensitivities in WIMP-nucleon interactions using liquid xenon time projection chambers (TPCs), first with the XENON10 and later with the XENON100 experiments. The actual phase of the experiment consists of an unprecedented one ton fiducial (three tons total) volume of ultra pure liquid xenon as both target and detection medium. The data-taking will start soon and should reach sensitivities down to 10-47 cm2 after two ton years of exposure. I will present the upgrade to the ton scale which was only possible due to a massive research and development program encompassing every aspect of the detector. The current and future stages of the XENON experiment in the context of the global dark matter search will also be discussed.
 

I shall present three important results on weak measurements. They are:

i) repeated weak measurements on a single copy can not provide any information on it and further that in the limit of very large such measurements, weak measurements have exactly the same characteristics as strong measurements.However, a number of interesting results can be obtained for joint probabilities for the random walks in the quantum state space under such repeated weak measurements.,

ii) the apparent non-invasiveness of weak measurements is no more advantageous than strong measurements in the specific context of Leggett-Garg measurements when errors are properly taken into account and finally,

iii) weak value measurements are optimal, in the precise sense of Wootters and Fields, when the post-selected states are mutually unbiased with respect to the eigenstates of the observable whose weak values are being measured. Furthermore, notion of weak value coordinates for state spaces are introduced and elaborated. It is shown that the metric on the state space in these coordinates is conformal. 

Around 1979 there were controversies about the validity of the Einstein Quadrupole Formula for gravitational radiation raised by the work of Ehlers, Rosenblum, Goldberg and Havas. One of the motivations for this was the somewhat clumsy treatment of the problem by Einstein. Even the improved treatment found in Landau and Lifshitz had some lacunae.

I investigated this problem from the point of view of spin-2 theories in two different ways. One was a Feynman graph derivation(with V. Soni) based on the Einstein-Hilbert action. Second one was through the techniques of low energy theorems found to be very powerful in particle physics. The low energy theorems do not require any particular action, and they yield GR as the universal low energy limit. Both vindicated the Einstein formula.

In this talk I shall describe both approaches. I will also discuss how the low energy theorems work in other particle physics contexts. I will sketch how one can go beyond the leading order analyses for both electromagnetic and gravitational radiation. 

In this talk I first review the current status for neutralino dark matter after taking into account the results from the LHC and from direct and indirect dark matter searches. I then entertain the possibility that the dark matter candidate is the supersymmetric partner of a right-handed neutrino. In this scenario the dark matter is produced via the decay of the long-lived next-to-lightest SUSY particle and leads to distinctive signatures at colliders.

We devise a renormalization group analysis for quantum field theories
with Fermi surface to study scaling behaviour of non-Fermi liquid
states in a controlled approximation. The non-Fermi liquid fixed
points are identified from a Fermi surface in (m+1) spatial
dimensions, while the co-dimension of Fermi surface is also extended
to a generic value. We also study superconducting instability in such
systems as a function of dimension and co-dimension of the Fermi
surface. The key point in this whole analysis is that unlike in
relativistic QFT, the Fermi momentum $k_F$ enters as a dimensionful
parameter, thus modifying the naive scaling arguments. The effective
coupling constants are found to be combinations of the original
coupling constants and $k_F$.

In the time evolution of neutral meson systems, a perfect quantum coherence is usually assumed. The important quantities of the B(d) system, such as sin (2beta) and Delta m(d), are determined under this assumption. However, any real system interacts with its environment and this interaction can lead to decoherence. It is therefore desirable to re-examine the procedures of determination of sin(2beta) and Delta m(d) in meson systems with decoherence. We find that the present values of these two quantities are modulated by the decoherence parameter. Re-analysis of B(d) data from B-factories and LHCb can lead to a clean determination of decoherence parameter, sin(2beta) and Delta m(d).

There is compelling evidence for the existence of Dark Matter (DM) in the universe. After a review of this evidence and of the various types of searches which can be conducted to detect DM, the role of the LHC in the quest for this elusive particle will be explained. The various ways in which DM could be searched for at the LHC and the most recent results from the ATLAS experiment will be discussed.

I discuss the role of the torsion tensor in geometry in the case in which Dirac fields are considered, reviewing models in which the spin of particles is coupled to torsion: I will present some of the effects of the torsion-spin coupling for Dark Matter, neutrino oscillations and the cosmological constant problem.
 

Recently, deviations in flavor observables of B -> D(*) tau nu have been shown between the predictions in the Standard Model and the experimental results reported by BaBar, Belle, and LHCb collaborations. One of the solutions to this anomaly is obtained in a class of leptoquark model with a scalar leptoquark boson S_1, which is a SU(3)_c triplet and SU(2)_L singlet particle with -1/3 hypercharge interacting with a quark-lepton pair. With well-adjusted couplings, this model can explain the anomaly and be compatible with all flavor constraints. In such a case, the S_1 boson can be pair-produced at CERN's Large Hadron Collider (LHC) and subsequently decay as S_1 -> t tau, b nu, c tau. This paper explores the current 8 and 13 TeV constraints, as well as the detailed prospects at 14 TeV, of this flavor-motivated S_1 model. From the current available 8 and 13 TeV LHC searches, we obtain constraints on the S_1 boson mass for M_{S_1} < 400 GeV - 640 GeV depending on values of the leptoquark couplings to fermions. Then we study future prospects for this scenario at the 14 TeV LHC using detailed cut analyses and evaluate exclusion/discovery potentials for the flavor-motivated S_1 leptoquark model from searches for the (b nu) (b nu) and (c tau) (c tau) final states. In the latter case, we consider several scenarios for the identification of charm jets. As a result, we find that the S_1 leptoquark origin of the B -> D(*) tau nu anomaly can be probed with mass less than around 600/800 GeV at the 14 TeV LHC with 300/3000 fb^-1 of accumulated data.

The pion polarizability is of fundamental interest in the low-energy sector of quantum chromodynamics. It is directly linked to the quark-gluon substructure and dynamics of the pion, the lightest bound system of the strong interaction. COMPASS measured the electromagnetic polarizability of the charged pion, which describes the stiffness of the pion against deformation in strong electromagnetic fields. Previous low statistics experiments in Serpukhov (Russia), where the Primakoff method for realizing interactions of charged pions with  quasi-real photons was first employed. Later, other measurements based on photon-nucleon and photon-photon collisions were also carried out at different laboratories. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than previous results, roughly by a factor two, with the smallest uncertainties realized so far. The results are consistent with chiral perturbation theory predictions, and strength the identification of the pion with the Goldstone boson of the strong interaction.

The COMPASS Collaboration, C. Adolph et al. (2015). Measurement of the Charged-Pion Polarizability. Physical Review Letters, 114(6), 062002.

Biography: Murray Moinester, Emeritus Professor of Physics, received his Ph.D. from the
University of Rochester in 1968, and then joined the faculty at Tel Aviv University. He served
as guest professor for extended periods at many leading universities and accelerator
laboratories, has extensive experience in experimental and computational methods, carried out
many research programs in high energy particle and nuclear physics, published some 200
scientific papers in refereed journals, authored some 75 conference papers; worked as a patent writer, on water security via online IR monitoring of chemical hazards, in the field of Archaeology on infrared imaging & scientific dating, on statistics analysis for the social sciences, and on climate engineering.

The multiverses are a consequence of eternal inflation  where different regions that are causally disconnected expand as parallel universes or in a more conventional language, as independent bubbles. Thus, an interesting question, is to analyze whether this theoretical idea may or not leave observational traces or to provide a new approach to new cosmological problems. In this talk by using techniques of noncommutative quantum mechanics we will explore a possible mechanism analogue to the motion of charged particles moving in an external magnetic field.

In the Standard Model, the electroweak symmetry is broken by the vacuum expectation value of an isospin-doublet scalar field, i.e. the usual Higgs field.  But could part of the observed electroweak breaking be caused by scalar(s) with higher isospin?  The answer is yes, and the possibility can be tested now through searches at the LHC.  Such models generically predict doubly-charged and singly-charged exotic Higgs bosons that decay to W or Z boson pairs and play an essential role in the theoretical consistency of the models.  I'll discuss searches for these exotic Higgs bosons within the prototype Georgi-Machacek model and how they constrain electroweak breaking contributions from a broad class of higher-isospin models.

We investigate the role of pressure in a generalized Skyrme model. We introduce pressure as the trace of the spatial part of the energy-momentum tensor and show that it obeys the usual thermodynamical relation. Then, we compute analytically the mean-field equation of state in the high and medium pressure regimes by applying topological bounds on compact domains.
The equation of state is further investigated numerically for the charge one skyrmions. We identify which term in a generalised Skyrme model is responsible for which part in the equation of state. This is further compared with the Walecka model.

The absence of proton decay at expected energy scales, combined with an
understanding of the sphaleron solutions has led to reformulation of
baryogenesis as an intermediate scale effect arising from leptogenesis.  I
review the proposals for dynamical generation of the baryon asymmetry of
the Universe, including the role of the B+L anomaly of the Standard Model
and the sphaleron. Connection of the leptogenesis at intermediate scale to
measured parameters from neutrino physics is presented. The status of
various unified models such as left-right symmetric model and SO(10) model
are reviewed. In view of the LHC continuing to restrict the parameter
space for supersymmetric extension of the SM, the need for new sources of
CP violation, a key ingredient of leptogenesis mechanisms, is hightened.

The future electron-positron International Linear Collider (ILC) has a
broad physics program covering topics such as precision measurements of
the Higgs Boson and possible detection of Dark Matter or supersymmetric
particles. New detector concepts have to be developed to meet the very
stringent requirements. For optimised event reconstruction innovative
Particle Flow algorithms will have to be applied to all detector systems.
 
The international CALICE collaboration is developing highly granular
calorimeter detectors to that purpose, among them the high granularity
Digital Hadron Calorimeter (DHCAL) 1m³ prototype, based on the Resistive
Plate Chamber technology, as developed at the Argonne National Laboratory.
Its 460,800-channel read-out makes it the first digital imaging
calorimeter ever.

The DHCAL prototype was first tested at Fermilab and CERN with different
absorber materials, such as steel and tungsten. In November 2011, test
beam data was taken without the additional absorber structures. Data
collected with minimal absorber material provides unprecedented insight
into the inner structure of both electromagnetic and hadronic showers. The
data set is ideal for detailed comparisons with GEANT4-based simulations.
Results of the measurements and comparisons with simulations will be
presented.

Neutrino physics entered a new era in the last decade. With the discovery of a non-vanishing
neutrino rest mass in oscillation experiments a variety of new questions showed up in the
context of nuclear and particle physics. One of the crucial questions is the determination of
the absolute neutrino mass, which cannot be measured in oscillation experiments. One option
is neutrino-less double beta decay, the simultaneous conversion of two neutrons into two
protons emitting two electrons. This total lepton number violating process requires that
neutrinos are their own antiparticles and is considered to be gold plated. Furthermore, the
measured half-life is directly linked with the neutrino mass. Currently, half-life measurements
beyond 1025 years are discussed. This requires a large amount of the isotope of interest and a
reduction of disturbing background to the smallest possible level. Indeed it is a search for the
needle in a haystack.
After a general introduction into double beta decay and the physics of the COBRA
experiment based on CdZnTe semiconductors the current status and results will be presented.
This will be followed by an outlook for a large scale experiment

Flavour changing neutral current process, such as B → K^(∗)l⁺l⁻ where l = e⁺,μ⁺,τ⁺ or ν_l, are highly suppressed in the Standard Model (SM) with a branching fraction ranging between 10⁻⁵ and 10⁻⁷. These rare decays are forbidden at tree level and can only occur at lowest order via 1-loop diagrams. B → K^(∗)l⁺l⁻ provides a stringent test of the SM and a fertile ground for new physics searches. Contributions due to virtual particles in the loop allow one to probe, at relatively low energies, new physics at large mass scales. The BABAR experiment at the SLAC National Accelerator Laboratory has completed data taking, with 424 fb⁻¹ collected at the Υ(4S) resonance. Using data from the BABAR experiment, I report the search for B → K^(∗)νν and its extension to charmonium resonance B → K^(∗)cc, cc → νν. BABAR’s results for B → K^(∗)l⁺l⁻ with l = e⁺ or μ⁺ are also discussed. Furthermore, the ongoing first search for B⁺ → K⁺ τ⁺τ⁻ is presented, along with its current status and anticipated sensitivity.

Le séminaire passera en revue certains des résultats majeurs du Run I au LHC et discutera des conséquences pour la physique HEP,  la cosmologie, et les perspectives à LHC run II et HL-LHC, avec emphase sur le secteur scalaire et les alternatives supersymétriques.

Among all the extra dimensional extensions of the Standard Model of particle physics (SM) at the TeV scale, 5D warped extra dimensions are the most attractive. Their first modern motivation was to address the Planck-weak hierarchy problem of the SM; the fact that there is a 15 orders of magnitude difference between the Planck scale (∼ 1018 GeV) and the weak scale (∼ 1 TeV). It was soon realized that the same mechanism that solves the Planck-weak hierarchy problem, can be used to explain yet another hierarchy of the SM; the hierarchy between the observed masses of the fermions, from the top quark ($m_t \approx 10^2$ GeV) down to the light neutrinos ($m_\nu \approx 5 \times 10^{−2}$ eV).

In this context, after introducing the model, I present the phenomenology of the Higgs boson at the Large Hadron Collider (LHC). I discuss that with simple modifications, the results are generically consistent with the current experimental results for new physics as low as 2 TeV, that is, within the reach of the LHC.

In this talk I'm going to explore a scenario where along with the observed scalar at 125 GeV we can still accommodate an additional scalar. I'll be focusing on the scalar called radion, which is an artifact of stabilizing the moduli of Randall Sundrum model. I'll also consider the mixing of radion with Higgs. I'll show that this observed scalar can not be an unmixed radion however, it can still be a mixed Higgs with mixed radion nearby. I'll also discuss a search strategy that can be used to discover a very light radion at the LHC.

Ref: JHEP10(2013)93 and 1410.0396[hep-ph]

In 1998 Type Ia supernovae observations first suggested that the recent Universe is accelerating. Further observations of Type Ia supernovae and also CMB, BAO etc. confirm the presence of a third component of Universe other than matter and radiation. Theoretically It needs new physics or modifications of earlier theory to be explained. Though the cosmological constant is the simplest solution, it has some theoretical problems. There are many alternative theories of gravity which can explain this late time acceleration. In this talk I will mainly discuss about the observation and theory of late time cosmic acceleration. First I will show how cosmological observations tell us about this kind of dynamics of the Universe and then talk about some theoretical models which can explain this acceleration. Motivations to look for alternative theories of gravity will also be discussed. 

I will discuss the notion of an effective, average, quantum mechanical path which is a solution of the dynamical equations obtained by extremizing the quantum effective action. Since the effective action can, in general, be complex, the effective path will also, in general, be complex. The imaginary part of the effective action is known to be related to the probability of particle creation by an external source and hence one expects the imaginary part of the effective path also to contain information about particle creation. We can identify such features using simple examples including that of effective path through the black hole horizon leading to thermal radiation. 

Let F be a two-photon entangled state where measurement by parallel polarization analyzers always yields opposite outcomes + and - for the left and right photons. If the analyzers are not parallel but oriented at an angle of 30^o to each other, the probability of obtaining the joint result ++ or -- on left and right is no longer zero but 1/2sin²30^o = 1/8, and if oriented at an angle of 60^o the probability of ++ or -- is 1/2sin²60^o = 3/8. In the Aspect experiment two entangled photons leave a source S and at the last instant are directed to one of two different analyzers:

				 A						B

				 0o						30o			
	

S

30^o 60^o
B C

Obviously if makes a difference to (say) the left photon when it is passing through analyzer B whether (i) its twin is passing through B or C, and (ii) what the outcome of the twin's measurement is. If it passes through B and emerges +, then the left photon cannot pass +, but if it passes through C and emerges + then the left photon should exhibit a probability 1/8 of being measured +.

Question: How is the behaviour of the left photon influenced by the distant measurement outcome of its twin? This is the famous problem of non-locality. Does nature permit faster-than-light signalling as a means of coordinating the outcome probabilities of the two photons? A physical branching space-time mechanism is described which permits a negative answer to this question. This mechanism explains the distant correlations of the Aspect experiment without recourse to local hidden variables, i.e. "instruction sets" for the two photons which tell them how to react when encountering analyzers set at various angles. 

Date: Wednesday, October 25, 2006

Time: 5:00 PM

Place: Concordia University, Loyola Campus, Science Pavilion (Building SP), 7141 Sherbrooke Street West, 3rd Floor 

Room: SP 365.01

Contact: 514-848-2424 ext 2595

Note: There are regular shuttle buses traveling between Sir George Williams Campus (1455 de Maisonneuve Blvd. W.) and Loyola Campus; see Shuttle bus schedule.

Many theories beyond the standard model predict the existence of a new massive neutral gauge boson called Z’. In this seminar, I will discuss the discovery and identification of such a Z’ with the ATLAS detector in the e+e- channel. First, I will review the different studied theoretical Z’ models coming from Grand Unified Theories and Extra-dimension scenarios. In a second part, I will show, using realistic detector parameterization, that the ATLAS discovery potential is very optimistic. Finally, I will discuss how to infer the underlying theory from a hoped Z’ discovery.

I will talk about a phenomenological model to describe D decays to pairs of pseudoscalars, and a pseudoscalar and a vector. The model parameters are tree level amplitudes for two body D decays. Assuming flavor-SU(3) symmetry we can extract these parameters by performing fits to known decay rates. I will describe how the model parameters may be used to study direct CP asymmetries in D decays. In light of the recent LHCb measurement of  ∆ACP ≡ ACP(K+K−) - ACP (π+π−) = [−0.82 ± 0.21(stat) ± 0.11(syst)]%,
I discuss an attempt to parametrize CPV in these channels using the earlier discussion of 2 body decays. If time permits, I will talk about some recent work on applying the 2 body results to extracting relative phases on Dalitz plots.

L’exposé portera sur le problème de la reconstruction d’une matrice densité d’un système d’atomes à trois niveaux. La dynamique d’un tel système gouverné par un Hamiltonien “raisonnable” mène à une division des types d’atomes en fonction des transformations accessibles au système. Cette division dépend de la distance entre les niveaux. Par exemple, pour un atome de type Ξ où les niveaux sont équidistants, les transformations induites par l’Hamiltonien sont des éléments du groupe SO(3) plutôt que du groupe plus general SU(3). Ce genre de restriction dynamique limite fortement les possibilités de reconstruction tomographique de la matrice densité du système.
  En général, on peut reconstruire complètement ou partiellement la matrice densité, soit en utilisant un ensemble continu ou un ensemble fini discret de transformations. Dans le cas discret, la solution optimale pour un atome générique est donnée en termes de bases mutuellement non–biaisées, qui sont elles-mêmes liées au sous-groupe de Pauli de SU(3). Dans le cas particulier de l’atome Ξ, les bases optimales du cas générique ne sont pas accessibles et on doit chercher une solution optimale sujette à une contrainte dynamique.

 When implemented using a reasonable Hamiltonian, the tomography of a three-level Ξ atom is complicated by the equidistant energy levels of the atom. This restricts the possible transformations to those in the SO(3) subgroup of SU(3). Although complete reconstruction is possible for a single Ξ atom using a continuous set of tomograms, the discrete optimal set of tomograms, related to mutually unbiased bases in dimension 3, are not accessible by time evolution. We discuss here the search for an optimal set of discrete basis states compatible
with the reduced SO(3) symmetry of the system.

Au cours de cette présentation, je donnerai une brève introduction à la Gravité Quantique à Boucle (GQB), une des théories proposées pour unir la gravitation à la physique quantique. Une telle théorie est nécessaire afin de décrire les situations physiques où les effets gravitationnels et quantiques sont ni l'un ni l'autre négligeables. La présence de petits trous noirs est une telle situation. J'expliquerai comment un modèle simplifié de GQB produit des petits trous noirs qualitativement différents des trous noirs Schwarzschildiens. En particulier ils sont sans singularités. J'enfilerai en proposant que la matière sombre pourrait être constituée de trous noirs ultra légers de cette sorte. 

Dark Matter as Ultra-Light Quantum Black Holes?
In this talk I will give a basic introduction to Loop Quantum Gravity (LQG), a candidate theory to unify gravitation and quantum physics. Such a theory is needed to describe regimes where both gravitational and quantum effects are strong such as in small black holes. I will explain how a simplified model of LQG produces qualitatively different black holes which are devoid of the afflictions normally present in black holes and how the elusive dark matter could be constituted of ultra-light versions of these black holes.

The ¹²C(α,γ)¹⁶O reaction is one of the most important reactions in stellar nucleosynthesis and, for that reason, has sometimes been called ‘the holy grail’ of nuclear astrophysics. I will give a brief status report on earlier measurements and then discuss a new approach, which will utilize a superheated droplet detector and the free electron laser at Duke University.

 I will give an introduction to the physics of one-dimensional quantum wires generically described by Luttinger liquid theory. I will then focus on transport through junctions (including superconducting junctions) of two or more quantum wires. Finally, I will end with a brief mention of pending problems in the quasi-one dimensional world.

PICASSO is a direct dark matter search experiment installed at SNOLAB, Canada. It uses droplets of superheated C4F10 as the active detector medium and is designed to search for spin-dependent WIMP interactions. In this talk I will discuss our result from last summer which substantially restricted the interpretations of the DAMA/LIBRA annual modulations in terms of spin-dependent interactions. I will also give some insights as to where we are heading in the future.

We show that there are crucial similarities in the physics of cosmic microwave background radiation (CMBR) anisotropies and the flow anisotropies in relativistic heavy-ion collision experiments (RHICE). We also argue that, following CMBR anisotropy analysis, a plot of root-mean square values of the flow coefficients, calculated in a lab fixed frame for RHICE, can yield important information about the nature of initial state anisotropies and their evolution.

Muon decay offers an opportunity to test the Standard Model of particle physics in a purely leptonic situation where more ambiguous strong interaction processes are essentially absent. The TRIUMF Weak Interaction Symmetry Test (TWIST) was designed specifically to improve by an order of magnitude the precision of the decay parameters r ,d , and Pμx derived from measured energy and angle distributions of positrons from polarized positive muon decay. It tests the V-A structure of the decay by comparing the parameters to those predicted by the Standard Model in an analysis permitting more general Lorentz-invariant local terms.
    Since the completion of data taking in 2007, a careful analysis has been carried out with the aim of improving upon earlier intermediate results, by reducing systematic uncertainties, estimating residual biases, and evaluating consistency checks. The total uncertainties, representing improvements of 9, 12, and 7 in r ,d , and Pμx respectively, as compared to pre-TWIST experiments, are dominated by systematic uncertainties. The analysis was blind with respect to the central values of the parameters, and the hidden parameters were revealed in late January 2010.
   The talk will describe muon decay and the way in which we measure it. The experimental apparatus and analysis procedures will be presented, with particular attention to the reduction of leading systematic uncertainties. The results of the blind analysis and their uncertainties will be shown along with implications and limitations for physics beyond the Standard Model.

It is known that topological solutions in gauge field theories can carry fermionic zero energy modes. In this case the presence of the zero-energy modes induces a fermionic charge on the background solution. This induced charge can have non-integer values. We have explored semi-classical solutions which are only metastable but can nevertheless carry fermionic zero-energy modes. These modes in turn can induce fractional fermion number. We show that as a result, a meta-stable configuration of bosonic fields in fact becomes stable. The result is shown to hold even when the coupled fermions are majorana and do not themselves carry a conserved fermion number.

Nous investigons, via les simulations de Monte Carlo, les propriétés non-perturbatives du modèle de Higgs abélien en 2+1 dimensions sans et avec le terme de Chern-Simons dans la phase de symétrie brisée dans la limite de couplage fort, en termes de ses excitations topologiques: vortex et anti-vortex. L'intégral fonctionnel peut être approximé à une sommation sur des configurations de boucles de vortex fermées caractérisées par leur longueur (L) et leur masse (Mu). Le but du présent travail est de rechercher les phases possibles du système dans ce secteur, particulièrement, le potentiel de confinement induit entre les charges externes trouvé par Samuel et d'étudier l'effet du terme de Chern-Simons sur ce dernier.
   Nous avons formulé une description sur réseau du modèle effectif en utilisant une tesselation tétrédrique de l'espace tridimensionnel Euclidien pour générer des boucles de vortex fermées. En présence du terme de Chern-Simons, dans une configuration donnée, nous avons formulé et calculé le nombre d'enlacement entre les différentes boucles de vortex fermées.
   Nous avons analysé les propriétés du vide et calculé les valeurs moyennes de la longueur moyenne des boucles, de la boucle de Wilson et de la boucle de Polyakov à différentes températures en fonction de la masse des vortex. En présence du terme de Chern-Simons, nous avons analysé aussi la boucle de t'Hooft.
  Dans cette conférence, je présenterai notre modèle effectif de boucles de vortex fermées et sa description sur le réseau tridimensionnel de tesselation tétraédrique. Nos résultats seront présentés et discutés.

 The discovery of neutrino oscillation and neutrino mass by the Super-Kamiokande and SNO experiments opened a new era in neutrino physics. The T2K, Tokai-to-Kamioka long baseline neutrino oscillation experiment in Japan, aims at measuring the remaining neutrino mixing angle q13, and observe CP violation in the neutrino sector if q13 is large enough.
    The commissioning of the T2K detectors and beamline started in December 2009 and first neutrino events have been observed in the near detector. I will describe the status of the T2K experiment future plan.

Metastable vacua appear in many models of high energy physics such as supersymmetry breaking models. Stability of the false vacua against quantum tunneling is usually assumed to be sufficient to ensure viability of such models. In this talk, I discuss a new type of classical instability of the false vacuum when topological solitons are present. If the topology of the vacuum manifold allows for the existence of defects such as cosmic strings or monopoles, the true vacuum can be "seeded" within the cores of these defects and render the false vacuum parametrically unstable. I discuss two recently published examples of such instabilities.

 According to a conjecture attributed to Polya and Hilbert, there is a self-adjoint operator whose eigenvalues are the the nontrivial zeros of the Riemann zeta function. We show that the near-horizon dynamics of a massive scalar field in the Schwarzschild black hole spacetime, under a reasonable boundary condition, gives rise to energy eigenvalues that coincide with the Riemann zeros. In achieving this result, we exploit the Bekenstein conjecture of black hole area quantization, and argue that it is responsible for the breaking of the continuous scale symmetry of the near horizon dynamics into a discrete one.

Présentation du trajectomètre du détecteur ATLAS, une des expériences du Large Hadron Collider (LHC) situé au CERN, et des projets de mise à jour du détecteur pour son opération à haute luminosité du point de vue de la conception de détecteurs silicium et de leur électronique de lecture associée. Les méthodes de conception, de caractérisation et d'optimisation des détecteurs silicium et du détecteur interne en entier seront présentées. Un survol des différentes technologies de détecteurs (3D, planaires, diamants) et d'électronique (intégration 3D,SLID,SOI, 90-130 nm) sera aussi présenté.

 L'expérience VERITAS consiste en un réseau de quatre télescopes de 12m à imagerie Cherenkov et est situé dans le sud de l'Arizona. Les télescopes ont été concus pour observer les rayons gammas de très haute énergie (entre 100 GeV et plusieurs TeV). VERITAS permet d'étudier un vaste éventail de phénomènes astrophysiques incluant la recherche indirecte de matière sombre, l'origine des rayons cosmiques, les trous noirs et leurs jets relativistes, etc... L'expérience est complètment opérationnelle depuis deux ans. Je présenterai l'expérience ainsi que les résultas des récentes observations.

We consider the problem of the causal propagation of spinning fields, and how for these fields the spin-torsion interaction can cause problems; these problems may be acausal propagation or failure to propagate, or even loss of constraints needed to provide the correct number of degrees of freedom for the field: we discuss a few examples.

Little Higgs models are an attempt to realize the Higgs as a pseudo-Goldstone boson. In this talk I will review the structure of little Higgs models and present the difficulty related to electroweak precision measurements. Finally I will discuss the difficulty and present possible solutions to the construction of UV complete little Higgs models with T-parity.

Final states with high-pT leptons and jets are predicted by many Beyond the Standard Model (BSM) scenarios including leptoquarks, Left-Right Symmetry, various implementations of Grand Unification Theory (GUT), and other models. Such theoretical models extend the application of Quantum Field Theory to energies far above the Electroweak Symmetry Breaking (EWSB) energy scale and seek to provide a much more elegant and symmetric description of the fundamental forces. The implications of such models include possible answers to the origins of flavor, CP violation, baryogenesis, and other fundamental questions beyond EWSB. This work describes the study of leptoquarks in dilepton-jets final states in proton-proton collisions at a center of mass energy of 14 TeV using ATLAS apparatus at the Large Hadron Collider at CERN. The presented analysis is based on fully-simulated data samples that contain two or more high-pT lepton candidates and jets for an integrated luminosity of 100 / pb . Signal event selection, analysis algorithms, and suppression of SM backgrounds are discussed. ATLAS can discover leptoquarks up to masses of 565 GeV at 100 / pb for a branching ratio = 1 at a 5 sigma significance level.

 In this talk we will present scenarios of beyond the Standard Model where the signatures include many leptons (4 or more), no missing energy and large production cross section. Scenarios with such attractive phenomenology include supersymmetry, technicolor and extra-dimensions. We will also discuss the LHC prospects to discover or exclude those scenarios with less than 1 fb-1 of 10 TeV data.

Discovering the mechanism of electroweak symmetry breaking is one of primary goals of the Large Hadron Collider. Nature has hinted that the Standard Model (SM) cannot account for phenomena, and new models Beyond the SM (BSM) have been developed to address the shortcomings of the SM. After reviewing the current state of BSM Higgs searches at the Tevatron, I describe the prospects for BSM Higgs searches at the ATLAS experiment.

 Even a direct observation of a Higgs particle at the LHC will not suffice to tell us whether it is the standard model (SM) Higgs or not. An understanding of possible scalar/pseudoscalar new physics (SPNP) interactions through indirect means is therefore extremely crucial. We study the decays B→ K µ+ µ- and B_s → µ+ µ-assuming only SPNP. We show that any large deviation in Br(B → K µ+ µ-) from its SM prediction is not possible. Also, the maximum possible forward backward asymmetry of muons in B → K µ+ µ- allowed by the present upper bound on Br(B_s → µ+ µ-) is about 1% and hence will be very difficult to measure. On the other hand, Br(B_s → µ+ µ-) fails to put any constraints on longitudinal polarization asymmetry (ALP) in B_s → µ+ µ- which can be as high as 100% even if Br(B_s → µ+ µ-) is  close to its SM prediction. The measurement of ALP will be a direct evidence for an extended Higgs sector, and combined with the branching ratio it can even separate the new physics scalar and pseudoscalar contributions.

 It is widely believed that existing electroweak data requires a Standard Model (SM) Higgs to be light, while electroweak and flavour physics constraints require other scalars charged under the SM gauge couplings to be heavy. New Higgs-like scalars that are also colour octets -- well-motivated in the sense that they arise in models having approximate custodial symmetry and minimal flavour violation -- provide counter-examples to both of these statements since the scalars can be all simultaneously light (~ 100 GeV} or heavy (~ 1 TeV}, without running afoul of direct searches and electroweak precision measurements.

 The COMPASS experiment at CERN is running since 2002. Its main goals are to improve our knowledge of the nucleon spin structure, using a polarized muon beam and a polarized target, and to contribute to hadron spectroscopy using hadron beams and searching for "exotic" hadrons with constituent gluons.
   After a short overview of the two stage spectrometer, I will describe the present results on the gluon polarization in the nucleon. The versatility of the COMPASS spectrometer can contribute much more to the knowledge of nucleon structure. Further studies will be presented for the present data and future possibilities.

We discuss a dark matter (DM) scenario in an extension of a left-right symmetric model with a gauge-singlet scalar field. The gauge-singlet scalar can automatically become a DM candidate, provided that both P and CP symmetries are only broken spontaneously. Thus no extra discrete symmetries are needed to make the DM candidate stable. We give predictions for direct detection experiments, and  show that for some parameter range, the predicted WIMP-nucleon elastic scattering cross section can reach the current experimental upper bound.

I present the current status of the Cabbibo-Kobayaski-Maskawa matrix describing mixing and CP violation in the quark sector. I review the main ingredients of the standard global analysis, with an emphasis on the recent B-factory results and their theoretical interpretation. I describe the main hints of a tension between the various sources of information. I discuss the role of uncertainties, on the theory side from lattice gauge simulations, and on the experimental side from bias effects. Using the same approach, I consider and constrain a straightforward extensions of the Standard Model from data in flavour physics : the case of New Physics affecting neutral meson mixing only (Delta F=2 processes).

Dans ce séminaire, je vais présenter mes travaux de doctorat. Je vais donc discuter dans les grandes lignes des résultats de quatre projets de recherche. En premier lieu, je vais présenter une approche générale basée sur les contractions de Wick des opérateurs effectifs de désintégration des mésons B. Ceci est une alternative pour dériver des résultats généraux déjà connus. En second lieu, je vais présenter une nouvelle méthode pour extraire l'angle alpha du triangle unitaire à partir des mesures de B_d --> K0 K0bar. Troisièmement, je vais présenter les résultats d'une étude qui vise à déterminer si le modèle de Grossman-Neubert-Kagan (SUSY) peut accomoder le "B --> pi K puzzle". Finalement, je vais discuter d'une étude sur la nouvelle physique dans les désintégrations B --> phi K_s et B --> phi K*.

   *The seminar will be in English !!

I will discuss the context of my recent Physical Review Letter on the search for Large Extra Dimensions in the ppbar collider at Fermilab. 
The idea of Large extra dimensions is an attractive alternative theory for explaining the hierarchy problem. I will ty to motivate the need for such a theory and briefly explain the salient features of this theory. I will then describe the search for these extra dimensions with 1.1 fb-1 of Tevatron data. Since we have not observed any Large extra dimensions with the present data, we have proceeded to set limits on the parameters of this theory. I will discuss the techniques used to analyze the data, the signal Monte Carlo used to model the theory, various systematic uncertainties that went into the analysis, and the technique used to set limits on the parameters of this theory.

L’annonce faite récemment par l’expérience PAMELA d’une observation d’un flux anormal de positrons a fait couler beaucoup d’encre. Plusieurs y cherchent une explication venant soit de l’astrophysique, soit de la physique des particules. Une possibilité serait que cela soit dû à des annihilations de particules de matière noire. Certains théoricien-ne-s ont même suggéré une nouvelle théorie qui résoudrait non seulement le cas de l’observation de PAMELA, mais aussi cinq autres anomalies rapportées ces dernières années. Je ferai le point sur ces anomalies puis je montrerai comment cette nouvelle théorie pourrait les résoudre toutes du même coup. Mais cela implique l’existence d’un monde parallèle, une vallée cachée, dont on ignore encore tout. Je terminerai en montrant comment cette hypothèse peut être testée dès aujourd’hui avec différents collisionneurs. 

Much has been written over the past few months following the observation reported by the PAMELA experiment of an anomalous flux of high energy positrons. Many models, both from astrophysics and particle physics, have attempted to provide an explanation to this observation. Many have claimed this could be due to dark matter annihilation. But some theorists have even proposed a new theory that attempts to resolve in one go all known anomalies reported in astrophysics over the recent years. I will first review these anomalies, then will describe this new theory and show how it offers interesting and exciting possibilities in the context of Hidden Valley models. I will conclude showing how this could be tested at existing hadron and e+e- colliders.

(This talk can be presented in English if requested by the audience.)

seminar broadcast on evo  Community: Universe
    Meeting URL:  http://evo.caltech.edu/evoGate/koala.jnlp?meeting=eneueMvDv9a8a8I8alIn …: Montreal    
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I discuss the motivation, the implications, and the search strategies for a fourth family, in reverse order.

s-channel resonances are predicted by many models of Physics Beyond the Standard Model and it is quite possible that such an object will be discovered in the early years of the LHC program. If this occurs, the task will be to understand its origins. A brief survey of models that predict s-channel resonances will be given, concentrating mainly on extra neutral gauge bosons (Z' 's) arising from extended gauge theories. This will be followed by a description of how to search for a Z' and the resulting Z' discovery reach of the LHC. I will describe various diagnostic measurements to study Z' 's and describe some new observables we have proposed that can distinguish between models that take advantage of the ability to tag 3rd generation fermions

In the late sixties, T.D. Lee and G.C. Wick realized that the use of states with negative norm (complex energy) could remove the divergences found in QED when one attempted to compute mass differences between different hadrons in the same isospin multiplet. However, it was known that the use of such states could lead to inconsistencies with the unitarity of the S-matrix. Lee and Wick found a way to avoid formally this difficulty at the cost of introducing violation of microcausality (only detectable at short time scales). A couple of years ago, B. Grinstein, D. O'Connell and M. Wise built a model based on Lee and Wick's ideas. The "Lee-Wick Standard Model", as the authors named it, cures the quadratic divergence associated with the Higgs mass (hierarchy problem) by appealing to a cancellation mechanism that uses negative-norm states. The model becomes in this way a possible extension of the Standard Model to be probed in future experiments. In this talk, we will review the foundations of Lee and Wick's original proposal making emphasis on the unitarity and causality issues. We will study next the solution to the hierarchy problem in the Lee-Wick Standard Model and learn about the particle content and the interactions of this theory. Finally, we will analyze some of its phenomenological aspects, like experimental signatures of Lee-Wick particles at the LHC, constraints from electroweak precision tests and, perhaps, something else.

A fifty-year old apparently paradoxical thought experiment, involving two accelerating spaceships and a thread that connects them, states that the thread breaks due to length contraction. It was revived by John Bell in a debate with colleagues at CERN in the seventies. This paradox still appears to be regarded by some physicists as a proof that (i) only physical bodies, but not space, undergo relativistic length contraction and (ii) there is a stress in the relativistically contracted body. However, a proper relativistic treatment of the paradox demonstrates that it is a manifestation of a specific relativistic acceleration phenomenon, which means that length contraction plays no role in the resolution of the paradox. It is also shown that no stress is involved in the length contraction effect.

Last year a conceptual design report was produced for a new experimental project, called "SuperB", which would aim to collect almost two orders of magnitude more data than the current generation of heavy quark-flavour experiments at existing particle accelerator facilities. The new accelerator, which would be hosted by the Frascati (LNF) laboratory in Italy, would exploit several novel design features permitting electron-positron collisions at unprecedented luminosities while maintaining a clean, low-background experimental environment. This facility would operate concurrently with the LHC at CERN and would provide very complementary sensitivity to physics beyond the particle physics Standard Model. In this talk, I'll describe the accelerator and particle detector concepts, present the physics motivation for such a project and discuss the status of the ongoing international review and efforts towards a full technical design of the project.

In this talk, I review the main methods for measuring CP violation in the B system. I then present the principal results, concentrating particularly on the several discrepancies with the predictions of the standard model. Although these disagreements are mostly not statistically significant, they are intriguing since they are all in b -> s transitions. Furthermore, taken together, their significance increases. Finally, I discuss several projects I have recently been involved in, all related to this hint of new physics.

L’arrêt du programme LEP (Large Electron Positron collider) a marqué la fin d’une étape importante dans la recherche sur les composants et les lois régissant la structure ultime de la matière. La conclusion des expériences du LEP est une description extrêmement cohérente de l’infiniment petit dans le cadre du Modèle Standard de la physique des particules. Parmi les phénomènes recherchés auprès du LHC (Large Hadron Collider), se trouve le boson de Higgs, dernière particule manquante prédite par le modèle standard. L’observation expérimentale d’un ou plusieurs bosons de Higgs permettra une meilleure compréhension des mécanismes de brisure de symétrie électrofaible. 



Dans le cadre du Modèle Standard, un doublet scalaire de Higgs est prédit donnant lieu à la présence d’une particule scalaire neutre. La masse du boson de Higgs n’est pas prédite théoriquement. Par conservation de l’unitarité des calculs de section efficace, la masse du boson de Higgs est limitée à 1 TeV. Les limites apportées à la masse du Higgs par les expériences LEP imposent une masse supérieure à 114.5 GeV. Le LHC permettra de couvrir le domaine de masse prédit par le Modèle Standard ce qui dans le cas d’une découverte permettra de valider le Modèle Standard. 



Mesurer un excès d'évènements dans un canal de recherche du boson de Higgs n'est pas suffisant pour prouver son existence : nous devrons mesurer le spin et la valeur propre de CP de cette nouvelle résonance. Les couplages du boson de Higgs aux particules du Modèle Standard devront être déterminés. 



Le canal de désintégration du boson de Higgs en deux photons est un canal très important pour un boson de Higgs léger et il bénéficie de la bonne résolution du calorimètre électromagnétique du détecteur ATLAS. Ce processus souffre cependant d'un faible taux d'embranchement, l'ensemble des canaux doivent être considérés. La production associée à un boson Z ou W a la plus faible section efficace mais bénéficie d'un bon rapport signal sur bruit de fond et peut donc être utilisé pour augmenter la signifiance statistique d'une possible découverte. Les processus de production associée permettra également la mesure des couplages du boson de Higgs aux bosons de l'interaction faible. 

With present and upcoming colliders like the Tevatron and the LHC (Large Hadron Collider), the origin of electroweak symmetry breaking (EWSB) will be explored up to the TeV scale. In the absence of a light Higgs boson (SM or supersymmetry) vector boson scattering will be the best probe for the study of the mechanism of EWSB. Here a Chiral Lagrangian (ChL) Model, inspired by pion scattering, is used to extrapolate to what may happen at LHC energies in such case. This scenario is explored with simulation tools to evaluate the sensitivity of the ATLAS detector to new physics.

It was shown that quantum metric fluctuations smear out the singularities of Green’s functions on the light cone [1], but it does not remove other ultraviolet divergences of quantum field theory. We have proved that the quantum field theory in Krein space, i.e. indefinite metric quantization, removes all divergences of quantum field theory with exception of the light cone singularity [2, 3]. In this talk, it is discussed that the combination of quantum field theory in Krein space together with consideration of quantum metric fluctuations, results in quantum field theory without any divergences.

[1] Ford H.L., Quantum Field Theory in Curved Spacetime, gr-qc/9707062.
[2] Gazeau J.P., Renaud J., Takook M.V., Class. Quant. Grav., 17(2000)1415, gr-qc/9904023.
[3] Takook M.V., Int. J. Mod. Phys. E, 11(2002)509, gr-qc/0006019.

The liquid, maintaining its liquid state above its boiling point is said to be superheated. Superheated drop (bubble) detector consists of drops of such superheated liquid suspended in another liquid holding medium. These are threshold detectors and the threshold energy depends on operating temperature and pressure. It serves as a useful detector in different fields of radiation detection, such as for neutrons and cold dark matter search. The intrinsic insensitivity to most undesirable backgrounds opens the advantage of using it as neutron dosimeter especially for accelerator site where there is a strong background of gamma rays. The estimation of energy of the incoming radiation, the nucleation parameter and the practical application of the detector will be discussed in this talk.

The physics program at the LHC includes precision tests of the Standard Model (SM), the search for the SM Higgs boson up to 1 TeV, the search for the MSSM Higgs bosons in the entire parameter space, the search for Super Symmetry, sensitivity to alternative scenarios such as compositeness, large extra dimensions, etc. This requires general purpose detector with excellent performance. ATLAS and CMS are general purpose detectors at the LHC. The detector performance and the prospects for discoveries are studied in various detector performance and physics working groups. In this talk, I will discuss the discovery prospects with early data, up to 100 inverse picobarns of integrated luminosity.

Notre Galaxie serait plongée dans un halo de matière sombre, cette nouvelle forme de matière qui semble être un ingrédient essentiel pour expliquer les mouvements des astres et des galaxies et l'évolution de notre Univers depuis de Big Bang. De son côté, la physique des particules a un candidat naturel pour ce nouveau type de matière stable: le neutralino, qui découle des théories supersymétriques qu'on cherchera dans les collisions à venir au LHC. Un point de convergence de ces deux domaines de la physique serait la détection, en laboratoire, de collisions entre des particules de matière sombre de notre Galaxie et des noyaux atomiques.
A travers le monde, plusieurs collaborations préparent de tels détecteurs. Le défi est de différencier ces très rares événements de l'important bruit de fond du à la radioactivité naturelle. EDELWEISS développe des détecteurs semiconducteurs en germanium refroidis à 20 mK qui rendent possible une mesure simultanée de l'énergie totale de la collision (par thermométrie) et de l'ionisation caractéristique de ce type de collision. La phase II de l'expérience a été récemment installée au Laboratoire Souterrain de Modane, dans un environnement bas-bruit radioactif. Une nouvelle génération de détecteurs simples mais très efficaces pour identifier les pollutions de surface est en cours de déploiement.

MINOS (Main Injector Neutrino Oscillation Search), is a long baseline neutrino experiment designed to search for neutrino oscillations using two detectors, one at the Fermi National Accelerator Laboratory, IL (Near Detector) and a second one at Soudan, MN (Far Detector). Aim of the experiment is the study of  n_µ®n_t  oscillations and in particular the measurement of the oscillation parameters, D m₂₃² and sin²(2q₂₃). In this talk I will present recent results from MINOS.

In this talk we discuss the construction of realistic quark mass matrices in the Randall-Sundrum warped brane world senario. This is an essential step towards gauging whether the RS senarios can be a suitable framework for flavour physics. The RS model was constructed to solve the heirarchy problem by introducing a Planck brane and a TeV brane in AdS space. The difference in scale is given by the warp factor and dimensionless couplings in 4D are of order unity. The observed hierarchy in quark masses are due to the different locations the quarks occupy in the 5th dimension. Recently it was found that electroweak precision measurements requires the extension of the Standard Model gauge group to SU(2)_L×SU(2)_R×U(1)_X as well as making this a bulk gauge symmetry. Within this we examine the various constructions of quark mass matrices and how they can be accomodated in the RS model. One interesting feature of the RS flavor models of this kind is that the rare decay of t → c(u)Z has a relatively large branching ratio ~ 10⁻⁵. We discuss how this can be used to test the various quark mass matrices in the RS model.

See the ATLAS-Canada Workshop website for details.

La performance des oscilloscopes s'est accrue rapidement ces dernieres années, la bande passant de 2GHz à près de 20GHz pour des oscilloscopes temps réel entre 2000 et 2006. La loi de Moore poursuivant son cours, on peut calculer à quel moment la performance rencontrera les limites fondamentales de la physique et quelles seront ces limites - ainsi que la manière de les contourner. En particulier, le concept d'oscilloscope hétérodyne sera abordé.
Par ailleurs, la calibration et l'utilisation des oscilloscope fait intervenir plusieurs méthodologies de physique. Plusieurs aspects seront analysés. En particulier, il est desormais possible d'incorporer une simulation électromagnétique complète dans la mesure d'un canal pour calculer les voltages et courants présents en un point éloigné du canal de mesure en temps réel.
La méthodologie de mesure du scintillement ("jitter") pour des phénomènes répétitifs ou quasi-répétitis sera abordé.

L'existence de la matière sombre est suggérée par des nombreuses observations astrophysiques. Cette matière exotique peut être composée de particules neutres et massives, telles que les candidats proposés dans le cadre des extensions supersymétriques au Modèle Standard. Ainsi, la détection directe, effectuée en mesurant le spectre de reculs nucléaires, est une possibilité qui suscite un grand intérêt. Dans le cadre du projet PICASSO, un détecteur à gouttelettes surchauffées de grande masse et haute pureté est utilisé pour la recherche de la matière sombre. La collaboration PICASSO a entamé l'installation d'un ensemble de 32 modules de détection (totalisant 3 kg de masse active) au montage souterrain à SNOLab, Sudbury. Nous présentons le fonctionnement du détecteur à gouttelettes surchauffées, le système d'acquisition de données, les mesures d'étalonnage et les résultats obtenus avec les premiers modules installés à SNOLab. À ce jour, le signal attendu pour la matière sombre n'a pas pu être mis en évidence. Toutefois, ces mesures ont permis d'imposer des limites d'exclusion plus performantes que celles obtenues antérieurement.

I present a theoretical analysis of the phase diagram of Josephson junction arrays in the presence of charge and magnetic frustration. Using a dual description I show that the fundamental constituents of this theory are electric and magnetic excitations and that their condensations lead to a plethora of possible phases. The new formulation points out to the emergence of a rich phase diagram not attainable by standard mean field theory approaches. In addition to the usual superconducting and insulating states, I find, in the bilayer system, states exhibiting Hall quantization coexisting with interlayer coherence, states with Hall quantization without interlayer coherence and interlayer coherent states without Hall quantization.

Since the top quark's discovery in 1995, there have been several measurements of the top quark's mass and pair production cross section.
Due to this quark's special role in electroweak symmetry breaking, properties such as its charge should also be measured. I will give a brief introduction about the top quark in the context of high energy physics and present the first CDF measurement of the top quark's charge using its decay products from a sample of ~1 fb-1 of data collected with the CDFII detector at Fermilab's Tevatron collider. The standard model predicts the top quark charge to be +2/3 but alternative theories allow a fourth generation exotic quark with a charge of -4/3. The CDF data provides more insight into the true nature of the top quark and its impact on the standard model.

The Mini Booster Neutrino Experiment (MiniBooNE) at Fermilab is searching for the neutrino oscillations indicated by the LSND experiment. Confirmation of this mode of oscillation would indicate a break from the Standard Model of particle physics. Such new physics could take the form of heretofore unseen sterile neutrinos or exotic forms of symmetry breaking that would dramatically change the landscape of particle physics. MiniBooNE finished data-taking in neutrino mode in 2005 and is now taking data with a primarily anti-neutrino beam. Analysis of the neutrino data is in its final stages with results expected soon.

The measurement of the top quark mass is one of the flagship measurements to be performed at the Collider Detector at Fermilab (CDF). Indeed, a precise determination of this fundamental parameter of the Standard Model can be used to predict the Higgs boson mass that still eludes detection to date. I will present a precise measurement of the top mass that uses hadronic W boson decays to constrain the main systematic uncertainty of the measurement: the jet energy scale.



The attention of the hadron collider physics community is gradually shifting toward CERN where the first proton-proton collisions of the Large Hadron Collider (LHC) are expected in 2007. Intense activities are taking place to prepare the LHC experiments, like ATLAS, for the first period of data taking. I will present two examples of such activities in ATLAS: the final preparation of the pixel detector and the development of the data streaming model.

Top quarks were first observed in ttbar pair production in 1995. Ever since, the Tevatron experiments have been looking for the electroweak production of single top quarks, also predicted by the standard model. Single top quark events can be used to study the Wtb coupling, to measure the magnitude of the CKM matrix element Vtb without assuming only three quark generations, or as a source of polarized top quarks.

I will present the first evidence for the production of single top quarks with the D0 detector at the Fermilab Tevatron proton-antiproton collider. Individual top quarks are expected to be produced in association with bottom quarks through the exchange of a W boson (tb channel), or via the W-gluon fusion process (tqb channel). After applying selection criteria to the data, the signal-to-background ratio is improved with an algorithm to identify jets originating from a b quark. On the remaining data, several multivariate techniques are used for both production channels. I will describe the background model and analysis techniques. The most sensitive analysis, using boosted decision trees, gives a cross section sigma(ppbar --> tb + X, tqb + X) = 4.9 ± 1.4 pb with a significance of 3.4 standard deviations. The cross section measurement is used to directly determine for the first time the CKM matrix element Vtb without requiring 3 families of quarks or CKM matrix unitarity.

We study black hole and black brane solutions in brane theories with flat extra dimensions in Einstein gravity. Black hole solutions are found using an expansion in the ratio of the radius of the horizon, m, and the circumference of the compact dimension, L. We also investigate the thermodynamics of static black objects such as black holes, black strings and their generalizations to D dimensions (`black branes') in a gravitational theory containing the four dimensional Gauss-Bonnet term in the action, when D-4 of the dimensions are compactified on a torus. The entropies of black holes and black branes are compared to obtain information on the stability of these objects and to find their phase diagrams. We demonstrate the existence of a critical mass, which depends on the scale of the compactified dimensions, below which the black hole entropy dominates over the entropy of the black membrane.

A standard heuristic argument in general relativity textbooks for associating gravity not with a force but with curvature of space-time concerns the phenomenon of gravitational redshift of clocks. Yet there are distinct ways in which Pound-Rebka-type experiments are interpreted in the literature, and distinct ways in which the notion of curvature is related to redshift. A related argument common to a number of recent textbooks is found wanting. 

Note: Professor Harvey Brown is the Strategic Knowledge Cluster TaU (Time and Universe) Lecturer for 2006. The lectures are sponsored by SSHRC (Social Sciences and Humanities Research Council of Canada).

Date: Thursday, November 9, 2006 

Time: 4:00 PM

Place: Concordia University, Loyola Campus, Science Pavilion (Building SP), 7141 Sherbrooke Street West, 3rd Floor 

Room: SP 365.01

Contact: 514-848-2424 ext 2595

Note: There are regular shuttle buses traveling between Sir George Williams Campus (1455 de Maisonneuve Blvd. W.) and Loyola Campus; see Shuttle bus schedule.

I will describe a midi-superspace quantization scheme for generic single horizon black holes in which only the spatial diffeomorphisms are fixed. The remaining Hamiltonian constraint is remarkably simple, and in the vacuum case yields an infinite set of decoupled eigenvalue equations: one at each spatial point. The corresponding operator at each point is the product of the outgoing and ingoing null convergences, and describes the scale invariant quantum mechanics of a particle moving in an attractive $1/X^2$ potential. The variable $X$ that is analoguous to particle position is the square root of the conformal mode of the metric. The theory is quantized via Bohr quantization, which by construction turns the Hamiltonian constraint eigenvalue equation into a finite difference equation. The resulting spectrum gives rise to a discrete spatial topology exterior to the horizon. The spectrum approaches the continuum in the asymptotic region.

The project SIMPLE (Superheated Instrument for Massive ParticLE Experiments) is one of the two experiments (with PICASSO) to search for evidence of spin-dependent WIMPs using s superheated droplet detector. I will describe the SIMPLE experiment and its future plans including a brief review on a new type of SDD: CF3I.

We do not know why an accelerating body resists its acceleration. But if the worldtubes of physical bodies are real four-dimensional objects, the open questions of inertia and mass (as the measure of resistance a body offers to its acceleration) can be viewed from an unexpected point of view. As the worldtube of an accelerating body is deformed (is not geodesic) it seems natural to assume that there is a four-dimensional stress in the deformed worldtube of the body, which gives rise to a restoring force that resists the deformation of the body's worldtube and tries to restore its geodesic shape. This restoring force would manifest itself as the inertial force.
Calculations of the restoring force in the case of the classical electron and semiclassical calculations in quantum field theory show that the restoring force does have the form of the inertial force.

Time Reversal Invariance (T) , with its origins in microscopic reversibility, has received renewed interest in modern physics as a constituent of CPT symmetry. CP symmetry and T symmetry also play a role in the models of primordial synthesis. So far, CP and T violations are found only in neutral meson sectors (K0 and B0 decays) and the amount of CP violation, while accounted for by the Standard Model (SM), is not enough to describe baryogenesis. This situation, along with other unsatisfactory features of the SM, makes it necessary that we find additional sources of CP (T) violation.  
   Following the suggestion by Sakurai, transverse polarization measurements in K-decays were carried out over several years as a test of the T-invariance. The latest measurement was the E-246 experiment at the 12 GeV proton synchrotron of the National High Energy Accelerator Research Organization (KEK), Tsukuba, Japan. I will present the measurement details and the final results of this experiment.
   The construction of a high intensity 50 GeV proton accelerator (J-PARC), a joint project of Japan Atomic Energy Research Institute and KEK, gives us an opportunity to do an experiment with at least about 20-fold increase in sensitivity. A proposal to perform such an experiment with an upgraded E246 detector is being prepared. I will present these details and anticipated physics outcomes.

The next generation of Cosmic Microwave Background (CMB) experiments will open a new window on the universe. By making precision measurements of the CMB polarization on large angular scales, we may see signature of inflation carried by gravity waves. Through measurements of temperature anisotropy on small angular scales, we can discover distant galaxy clusters, constraining dark energy by providing a measure the universe's expansion history. These advances are made possible by new technology. I'll discuss the next generation of CMB experiments that employ recent advances in detector, readout, and cryogenic technology. These experiments are reaching the field now.

The first generation of stars produced energetic photons, thereby ionizing the thitherto neutral universe. The ionization effectively worked as a veil, obscuring correlations in the Cosmic Microwave Background (CMB) on small angular scales. In parallel, the first generation of stars also ejected large amounts of dust - thereby laying ground for the coming generation of stars. The dust also covered the CMB somewhat, particularly where the matter density was high. The objective of this presentation is to explain the importance of this early dust.

The presentation will be in English but I will be happy to answer any question in French.

Neutralinos are prime candidates to constitute the dark matter of the universe. Recent high-precision measurements of the dark matter density and prospects for detecting present-day dark matter annihilation byproducts motivate the calculation of the neutralino annihilation cross section beyond leading order. I'll review our recent calculation of QCD corrections to neutralino annihilation into gluon pairs and sketch possible future directions. The calculation makes use of some nice theoretical techniques, from the proper treatment of Majorana spinors to the use of the Adler-Bardeen theorem to relate neutralino annihilation to pseudoscalar decay. It turns out that our corrections are unimportant for the relic density calculation but could have an order-one effect on present-day neutralino annihilation rates.

In this talk, we shall motivate the existence of new physics from present neutrino data. In contrast to quarks, neutrino data indicate large leptonic mixings with tiny masses. The well known seesaw mechanism explains small masses but needs additional inputs to explain large mixings. We shall discuss two very simple proposals based on the seesaw mechanism that do the job. We then use the Left-Right model (which naturally incorporates seeesaw) to connnect physics at electroweak scale to B-L breaking scale that is also consistent with current baryon asymmetry. Finally, we shall conclude with a road map for future prospects that correlates data from astro-physics to colliders.

There is strong evidence for cold dark matter in the universe. One of the prime candidates for dark matter is the lightest supersymmetric particle. We examine the implication of cosmological observations on different supersymmetric models and discuss the implications for collider physics and for direct searches.

A new and intuitive perturbative approach to time-dependent quantum mechanics problems is presented, which is useful in situations where the evolution of the Hamiltonian is slow. The state of a system which starts in an instantaneous eigenstate of the initial Hamiltonian is written as a power series which has a straightforward diagrammatic representation. Each term of the series corresponds to a sequence of "adiabatic" evolutions, during which the system remains in an instantaneous eigenstate of the Hamiltonian, punctuated by transitions from one state to another. The first term of this series is the standard adiabatic evolution, the next is the well-known first correction to it, and subsequent terms can be written down essentially by inspection. Although the final result is perhaps not terribly surprising, it seems to be not widely known, and the interpretation is new, as far as we know. Application of the method to the adiabatic approximation is given, and some discussion of the validity of this approximation is presented. 

Large strides have been made in the past decade in the experimental understanding of neutrino masses and mixings, yet the incredible smallness of the neutrinos’ masses remains a theoretical puzzle. Theorists have long postulated that the solution to this puzzle could provide valuable clues to the structure of physics at very high energy scales. The left-right model of particle physics provides an intriguing solution to the puzzle through the so-called “seesaw mechanism.” The talk begins with an analysis of the Higgs sector of the model. A horizontal symmetry is employed in such a way that the symmetry scale can be kept relatively low – of order 10’s of TeV. The end of the talk returns to a phenomenological study of neutrinos in the left-right model.

The phenomenology of B decays into two vector mesons offers the possibility of measuring many observables related with the angular distribution of the final outgoing particles. Here we study in particular decays into Phi K* states, which can be used to disentangle annihilation contributions to the amplitude and to look for effects of physics beyond the Standard Model through CP violating observables. We show that the analysis also serves as a test of the consistency of the factorization approach.

The MSSM can explain electro-weak symmetry breaking if one scalar top quark (stop) is light. In addition, in this framework, the neutralino is a good dark matter candidate and for small stop-neutralino mass differences Dm £ 30 GeV, co-annihilation plays an important role to match the results from WMAP and SDSS for the relic density in the universe.  In this scenario, the stops mainly decay into charm and neutralino, making its discovery difficult at hadron colliders due to background and trigger limitations.We present results for the discovery reach of the ILC for a DM candidate as low as 0(5GeV) based on a realistic experimental simulation.

The absence of CP Violation in the strong interaction is generally referred to as the "strong CP problem". The most elegant solution is a minimal extension of the Standard Model by Peccei & Quinn which postulates the existence of a light pseudoscalar particle called the axion. The CERN Axion Solar Telescope (CAST) is an experimental search for axions which have been produced in the hot dense plasma of the sun via the Primakoff effect. It utilizes an LHC prototype superconducting magnet to convert the axions into visible low energy X-ray photons via the inverse Primakoff effect here on Earth. The latest results will be presented along with our plans for extending the axion mass range into a region which will challenge even more severely the current theoretical models.

Muon decay provides an excellent place to study the structure of the weak interaction. Since it is a purely leptonic process, many uncertainties deriving from the internal structure of the particles involved or from other interactions are reduced. TWIST measures with high precision the momentum and angular dependence of positrons emitted from the decay of polarized positive muons. I will describe the apparatus, some of the novel analysis techniques that we have employed, and our future goals. New results for the muon decay parameters r and δ will be presented, together with their implications regarding the spacetime symmetries of the weak interaction. References: J.M. Musser et al, Phys. Rev. Lett. 94, 101805 (2005), A. Gaponenkoet al, Phys. Rev. D. (Rapid Communications) 71 (2005). 

The Sudbury Neutrino Observatory (SNO) experiment has produced some of the most important results in physics of the last ten years. SNO data have been used to solve the solar neutrino problem and to conclusively prove that neutrinos undergo flavour change thus demonstrating that neutrinos have mass. These measurements require a fundamental change to the standard model of particle physics and have been at the forefront of the current surge of activity in neutrino physics.

   A brief introduction to the standard model of particle physics will be given with emphasis placed on the role of the neutrino and its properties. An historical description outlining the development of our knowledge of neutrino properties will be provided.  The SNO detector and calibration procedures will be described in detail along with presentation of the latest physics results from the complete salt-phase data set. The impact of these results will be discussed in the context of the solar neutrino problem, in terms of currently favoured neutrino models, and in conjunction with results from other neutrino experiments.  The final portion of the talk will explore the future of neutrino physics with focus centred on experiments that can significantly improve our understanding of neutrinos and their properties.

Several hints suggest that we are on the right track towards unification of the fundamental forces: the strong and electroweak coupling constants converge at energy scales of 10**16 GeV, if corrections due to Supersymmetry are included. "Dark matter", material completely unlike ourselves, yet making up 25% of the universe, may well be explained by a stable neutralino.

At the Large Hadron Collider (LHC) at CERN, starting in 2007, we will probe new physics such as SUSY in proton-proton collisions at 14 TeV, extending our reach by an order-of-magnitude over previous colliders. This talk will describe the wealth of physics to be discovered at the LHC, the challenges in building and commissioning the ATLAS detector, and the outlook for the future.

For 25 years the CLEO experiment at the Cornell Electron Storage Ring (CESR) was at the forefront of B-physics. During this time cutting edge results in charm physics were also produced - including the discovery of the Ds+, searches for charm mixing, and the study of charm meson dynamics. Recently, CLEO and CESR have been modified to run at charm production threshold. The CLEO-c research program will include studies of leptonic, semileptonic and hadronic charm decays, searches for exotic and gluonic matter, and test for physics beyond the Standard Model. Results from CLEO-c will improve our knowledge of the CKM matrix and extend the physics reach of the B-factories and the Tevatron.

La compréhension de la structure des noyaux atomiques et des propriétés de la matière nucléaire nécessite l'exploration d'états extrêmes des noyaux. Ces états jouent un rôle essentiel dans le cosmos et constituent des tests sévères de notre description de la matière nucléaire. Également la compréhension des processus de nucléosynthèse passe par l’étude de ces noyaux exotiques.

À l’aide d'un puissant accélérateur comme le cyclotron de 500 MeV de TRIUMF à Vancouver, nous bombardons des cibles de matériaux réfractaires. Les noyaux exotiques ainsi produit sont arrêtés dans le matériau cible qui est porté à haute température afin d’en extraire les atomes exotiques. Ensuite, à l’aide de sources d’ions spécialisées nous en produisons des faisceaux exotiques intenses.

Durant les dernières années, nous avons développé une source par ionisation laser. Cette source utilise le fait que chaque atome a des niveaux bien spécifiques. En sélectionnant les transitions laser nous pouvons ainsi exciter des niveaux spécifiques de cet atome jusqu’à ce que l’atome soit ionisé. Nous pouvons ainsi produire des faisceaux purs.

Luminescence in certain doped alkali halide crystals does not decay exponentially. The explanation (for the examples we study) lies in the formation of non-linear excitations called breathers which appear to live on two-dimensional KAM tori. Quantization of the breathers is accomplished using a stroboscopic method.

The idea that the universe is trapped on a membrane in some high-dimensional spacetime may explain why gravity is so weak, and could be tested at high-energy particle accelerators. There is great freedom in the choice of extra-dimensional models which can be built to achieve this, but one class of models is of particular interest: Supersymmetric Large Extra Dimension scenario (SLED). This is because it can provide a framework in which the cosmological constant problem could be solved. The goal of this talk is to briefly introduce the fundamental features involved in the SLED scenario and to discuss more closely its experimental test at the LHC. To this end, we first consider a general extra-dimensional scalar that appears  in SLED as a graviton superpartner and examine the sensitivity of the ATLAS detector to the bulk scalar couplings with quarks and gluons. Next, we identify the lowest-dimension interaction which is possible between Standard Model brane fields and this bulk scalar. This lowest-dimensional interaction is unique and exclusive to SLED models and involves a trilinear coupling between a Standard Model Higgs and the bulk scalar. We again identify the sensitivity of the ATLAS detector to such a coupling. We finally compute its influence on Higgs physics at the LHC.

As the available centre-of-mass energy increases, the study of multiplicity fluctuations in the products of inelastic collisions of elementary particles has become the study of the largest part of the cross-section. After a few historical remarks on the first investigations on the subject, some examples of successes and failures of the traditional perturbative theory approach in multiparticle dynamics will be illustrated. This will lead to the introduction of phenomenological models, with a presentation of the current status of the field within the Dual String Model and the Clan Model (Clan Structure Analysis), concluding with an outlook on future developments.

Les bolomètres avec mesure simultanée de chaleur et d'ionisation sont présentement les détecteurs les plus sensibles dans la recherche directe de la matière noire. Les limites obtenues par la collaboration Edelweiss avec cette technique sont pour l'instant les meilleurs resultats publiés. Je présenterai cette expérience et ses résultats, en les comparant avec ceux obtenus tout récemment par d'autres expériences utilisant aussi les techniques bolométriques (CDMS, CRESST). Je situerai ces résultats dans le vaste effort international en vue de développer des détecteurs pouvant être sensibles à la plus grande partie de la plage de taux prédits par les modèles supersymétriques, pouvant être aussi bas que quelques coups par tonne et par an, pour un seuil de détection de l'ordre de 10 keV.

Empty space is supposedly filled with energy! This is not based on an untested theory. Quantum Field 
Theory, the successful theory behind the Standard Model, tells us that there is energy due to quantum 
fluctuations in the vaccuum. This energy is in general everywhere and infinite. It is therefore part 
of a background. Energy measurements,  say of energy levels of atoms,  etc. are energies measured with respect to this background. The obvious question is, "are there cases where we expect this vaccuum  energy to be detectable?". The answer is yes. One is supposed to observe it in gravitation. The other case is when fields are constrained to boundaries, say between two plates. Then there is a difference between the infinite energy of empty space with boundaries and the infinite energy of empty space without boundaries. This difference is called the Casimir energy and it leads to a force between the two plates. One can make theoretical calculations of the Casimir energy and force. I will illustrate some simple examples. The experiments are difficult because the force is so tiny. I will briefly discuss some of the latest experiments.

Dans ce séminaire, nous ferons le point sur le projet de création d’un institut qui regrouperait des chercheurs, leurs étudiants et des industriels autour d’un projet commun qui serait de développer des technologies et des applications concrètes reliées au rayonnement. Ces technologies et ces applications seraient issues du fruit de recherches fondamentales et appliquées dans des domaines aussi divers que la sciences des matériaux, la physique et l’astrophysique des particules, l’électronique et l’imagerie médicale, cellulaire et industrielle, la biologie, la production d’énergie propre et la médecine clinique. Bien entendu, cet institut se devrait d’être appuyé par plusieurs dizaines de PME de la grande région de Montréal qui oeuvrent déjà dans ces technologies et dans ces marchés. Lors de ce séminaire, nous présenterons plus en détails la démarche qui a été entreprise et les principales étapes qui mèneront à la création de cet institut. Nous présenterons des exemples concrets sur la nécessité d’un tel institut dont le premier objectif serait de favoriser la créativité, la recherche, l’inventivité et la formation de personnel hautement qualifié.

La polarisation transverse du muon dans la désintégration K⁺ ® p⁰ m⁺ n offre une possibilité intéressante pour explorer la physique au delà du Modèle Standard. Cette polarisation est pratiquement nulle dans le Modèle Standard et les effets de l'interaction dans l'état final sont aussi tout à fait négligeables dans la désintégration en question. Une expérience, effectuée au laboratoire national japonais KEK, est sur le point de fournir un résultat final, une limite supérieure améliorée. 



The transverse polarization of the muon in the K⁺ ® p⁰ m⁺ n decay offers an interesting possibility to search for physics beyond the standard model. This polarization is practically zero in the standard model and the final-state-interaction effects are also negligible in the decay in question. An experiment performed at the Japanese national laboratory KEK will soon provide a final result, an improved upper limit.

The possibility that population III stars have reionized the Universe at redshifts greater than 6 has recently gained momentum with WMAP polarization results. We have analysed the role of early dust produced by these stars and ejected into the intergalactic medium. We show that this dust, heated by the radiation from the same population III stars, produces a submillimetre excess. The electromagnetic spectrum of this excess could account for a significant fraction of the FIRAS (Far Infrared Absolute Spectrophotometer) cosmic far infrared background above 700 micron. This spectrum, a primary anisotropy (D T) spectrum times the n² dust emissivity law, peaking in the submillimetre domain around 750 micron, is generic and does not depend on other detailed dust properties. Arcminute scale anisotropies, coming from inhomogeneities in this early dust, could be detected by future submillimetre experiments such as Planck HFI.

Thanks to the high collision energy and luminosity of the LHC, the ATLAS detector will be capable of revealing the existence of extra spatial dimensions in some substantial region of parameter space. I shall summarize recent studies from the collaboration on different possible signals predicted by models where the dimensions are "large", where they are of size ~TeV^-1 or where they are “warped”. I shall also mention studies on the potential for black hole production and detection.

The Fermilab Tevatron proton-antiproton Collider operates at a center-of-mass energy of 1.96 TeV (the highest energy frontier). The dilepton channel is sensitive to deviations from the Standard Model predictions and could signal new physics. In this talk I will describe an analysis of events containing two high-p_T leptons, missing transverse energy and jets. The analysis strategy consists on selecting and understanding a dilepton sample based on one "tight" lepton (either an electron or a muon) and a "loose" lepton (a high p_T isolated track without lepton ID). Understanding the contribution coming from various physics backgrounds (which yield two real leptons) and fake backgrounds in which a parton or gluon fluctuate into an isolated track) is critical to this analysis. A wide range of kinematic regions (various jet E_T and track p_T cuts) have been explored. Preliminary top quark pair cross-section measurement will be presented using a 200/pb data sample collected by CDF in Run II.

This presentation will focus on my thesis work on the 2 Higgs Doublet Model (2HDM) in the D0 experiment. I shall briefly present the D0 detector and discuss its performance, with particular attention on the liquid Argon calorimeter and its calibration. I shall then describe the 2HDM, for which lepton number violation is possible. We have constrained the coupling responsible for this violation with recent data on the muon anomalous magnetic moment. Then we have used these constraints to determine the discovery potential of the process H0/A0 -> tau muon with a full simulation of the D0 detector.

We review some basic experimental and theoretical concepts concerning nucleon-nucleon interactions, with focus on a QCD inspired model where high energy cross section rise with energy as a consequence of the increasing number of soft gluons populating the colliding particles.

Le Programme CERN-Gran Sasso

    Dans ce séminaire, je donnerai un aperçu du programme de physique envisagé avec le futur faisceau neutrino du CERN  appelé CNGS. Ce projet neutrino à longue distance a pour but principal de chercher l’apparition de n_t dans un faisceau de n_m de haute énergie, de façon à déterminer de manière non ambiguë l’origine du phénomène d’oscillations observé avec les neutrinos atmosphériques.
    Deux détecteurs massifs, OPERA et ICARUS, devraient être installés dans le laboratoire sous-terrain du Gran Sasso à 730 km de distance du CERN. Ils sont actuellement en construction et devraient permettre l’étude des propriétés des neutrinos issus du faisceau. L’état d’avancement des détecteurs et leurs performances pour les études des oscillations neutrinos, incluant l’oscillation  n_m "n_e, seront présentés.

The CERN-Gran Sasso Neutrino Program

In this talk, I  will review the current experimental program envisaged with the future CERN neutrino beam (CNGS). This long baseline neutrino project is designed to primarily search for n_t appearance in an high energy n_m beam in order to answer unambiguously on the origin of  the neutrino oscillations observed at the atmospheric Dm² scale.

Two detectors, OPERA and ICARUS, to be located in the Gran Sasso underground laboratory, 730 km from CERN,  are under preparation and should investigate the neutrino properties coming from the beam. The status of the detector preparation and the physics potential and performances for neutrino oscillation studies including n_m "n_e search will be presented.

ATLAS is one of two general-purpose detectors currently being built at the Large Hadron Collider, the next generation of proton-proton collider due to start in 2007. Due to the high rate of events as well as the large number of read-out channels, the trigger system for such a detector is quite challenging. ATLAS uses a three level trigger system where the first level is hardware based and the high level triggers are software based. This talk will present the physics motivation of the ATLAS detector and the chosen selection strategies for the trigger, the implementation of the High Level Trigger software and some related measurements.

The radion, an essential ingredient of models of Warped Quantum Gravity (non-minimal Randall-Sundrum (RS) model), is required to stabilize the size of the extra dimension. From the phenomenological point of view, it deserves special attention. In this talk I will describe one such phenomenological study in which we will put some bound on the radion vev v_R for the case of a light radion using the LEP2 lower bound on the Higgs mass.

Sphalerons in the Standard Model suggest the possibility that all the baryon asymmetry of the Universe could have been created at the electroweak scale. This relies on occurrence of bubble walls during the phase transition. In this talk we focus on an alternative mechanism for occurrence of nontrivial transient background configurations. We show that the domain walls accompanying the phase transition in the Left-Right symmetric model provide sufficient conditions for baryogenesis. It is then possible to derive conditions relating the scale of L-R breaking and the light neutrino masses suggested by the neutrino data.

Sphalerons in the Standard Model suggest the possibility that all the baryon asymmetry of the Universe could have been created at the electroweak scale. This relies on occurrence of bubble walls during the phase transition. In this talk we focus on an alternative mechanism for occurrence of nontrivial transient background configurations. We show that the domain walls accompanying the phase transition in the Left-Right symmetric model provide sufficient conditions for baryogenesis. It is then possible to derive conditions relating the scale of L-R breaking and the light neutrino masses suggested by the neutrino data.

On cherche des asymétries de brisure CP via les produits-triples dans les désintégrations non charmées des L_b a l'aide du modèle de factorisation. On a trouvé des résultats très intéressants dans le Modèle Standard qui nous ont encouragés à chercher les effets, sur de telles asymétries, de la nouvelle physique; et ce, en construisant un lagrangien efficace contenant tous les termes possibles.

Starting from recent observations about quasi-normal modes, we use semi-classical arguments to derive the Bekenstein-Hawking entropy spectrum ford-dimensional spherically symmetric black holes.  We find that, as first suggested by Bekenstein, the entropy spectrum  is equally spaced: 

       S_BH = ln(m₀) n 

where m₀ is a fixed  integer that must be derived from the microscopic theory. For d-dimensional black holes of radius R_H(M), our analysis predicts the  form of the unique quasinormal mode frequency in the large damping limit. This prediction has  been confirmed by recent calculations. These developments indicate that the classical quasi-normal modes are providing crucial information about the quantum gravitational states responsible for black hole entropy.

Nous mesurons la fraction apparente des configurations à quatre quarks dans un échantillon d'événements à quatre jets provenant des désintégrations hadroniques du boson Z, en comparant des correlations angulaires des quatre jets calculéesau deuxième ordre avec celles mesurées dans le détecteur OPAL*. Nous examinons la dépendance de R_4q, c.a.d. le rapport de la fraction apparente mesurée sur celle calculée, de plusieurs paramètres. Nous observons des excès  (R_4q > 1) en fonction de la somme des masses des deux jets les moins énergétiques, de la masse invariante des ces jets et en fonction du paramètre de résolution des quatre jets. Des modèles théoriques comme des éléments de matriçe couplés à des gerbes de partons produisent des excès qualitativement similaires. La possibilité que ces excès pourraient être compatibles avec une suggestion par Berger et al. (1), qui postulent l'existence de gluinos entre 12 et 16 GeV, est également examinée.



(1)  E.L.Berger et al., Phys.Rev.Lett.86 (2001) 4231.

*) Ces résultats préliminaires n'ont pas encore approuvés par la collaboration OPAL.





We measure the apparent fraction of four-quark configurations contained in a sample  of four-jet events from hadronic  decays of the Z boson by comparing leading order theoretical angular correlations of four-jet events with those of data obtained with the OPAL detector*. We investigate the dependency of R_4q, the ratio of the measured apparent  fraction of four-quark events over the predicted one, on several parameters. We observe enhancements (R_4q > 1) as a function of the sum of the intrinsic masses of the two least energetic jets, the invariant mass formed by these jets, and the four-jet resolution parameter. Models which include higher order effects such as combinations of matrix elements with a parton shower produce qualitatively similar enhancements. The possibility that these results might be compatible with a suggestion by Berger et. al (1), who postulate the existence of gluinos in the 12 to 16 GeV range, is also examined.



(1) E.L.Berger et al., Phys.Rev.Lett.86 (2001) 4231

* These preliminary results have not yet been endorsed by the OPAL collaboration.

The potential for the discovery of a Standard Model Higgs boson in the mass range m_H < 2m_Z in the vector boson fusion (VBF) mode has been studied for the ATLAS experiment at the LHC. I will show that the characteristic signatures of jets in the forward regions of the detector and of low jet activity in the central region allow for an efficient background rejection. I will emphasize the H → τ τ decay mode that has been studied using a realistic simulation of the expected detector performance and background processes estimation. Results on other decay modes and Higgs coupling parameters will be presented as well. These studies demonstrate the large discovery potential from the Higgs production in VBF and the unique opportunity of measuring its Yukawa coupling to fermions.

The Fermilab Tevatron proton-antiproton collider is the highest energy collider in the world, and will remain so until 2008, when the LHC at CERN turns on. Run II at the Tevatron is underway. Commissioning of the DZero experiment is nearing completion and the DZero detector is now collecting physics-quality data. In this talk, the Dzero experiment will be briefly described. The Silicon Track Trigger, a novel device for triggering on displaced tracks from b-quark decays, will be presented. The b-quark physics program at DZero will be discussed and recent results will be shown. Prospects of the B physics potential of DZero over the next few years will be illustrated, as will be the possibility of discovering the Higgs boson at the Tevatron.

The Sudbury Neutrino Observatory (SNO) has determined the flavor content of the ⁸B solar neutrino flux by measuring the rates of charged current and neutral current neutrino interactions on deuterium. These results directly demonstrate neutrino flavor transformation at greater than 5 σ significance. The total flux of ⁸B neutrinos is found to be in good agreement with solar model predictions. Measurements of the day and night neutrino energy spectra probe models of neutrino oscillation. A global fit of SNO data and results from other solar neutrino experiments to neutrino oscillation models strongly favors the Large Mixing Angle (LMA) MSW solution.

CompHEP software package and CompHEP-PYTHIA interface as powerful tools for High Energy Physics phenomenology are introduced. Various features and details of these programs will be presented along with the short tutorial. Examples of the CompHEP and CompHEP-PYTHIA interface applications for study of Standard Model physics and beyond will be shown.

The discovery of one or several Higgs bosons will be fundamental for a better understanding of the mechanism of electroweak symmetry-breaking. In the standard model, one Higgs boson is predicted, however the Higgs boson mass is not theoretically predicted. In supersymmetric theories, the Higgs sector is extended to contain at least two doublets of scalar fields, leading to the prediction of five physical Higgs particles. Present experimental limits on Higgs boson searches will be presented, followed by a discussion of the prospects of Higgs boson discovery at the LHC.

One of the main scientific questions that remains unanswered is the nature and behaviour of the "Glue" which holds the quarks together. The puzzling feature of this construction is that quarks are never found free, but only in triplets or pairs; that is known as "confinement". Since gluons carry colour charge, they can form chromoelectric flux tubes, which may result in glueballs or hybrid combinations of gluons and quarks. In certain models, the latter can be produced with JPC quantum numbers not allowed in the simple quark picture. An international experiment (GlueX) is being proposed to search for such exotic hybrid mesons at Jefferson Lab, Virginia, and thus elucidate the phenomenon of confinement. The GlueX program will be presented, with emphasis on the electromagnetic calorimeter R&D at the University of Regina, for which scintillating fibers are glued onto a lead matrix.

The new proposed experiment CLEO-c in the Wilson Laboratory at Cornell University will explore the physics potential of the CLEO detector and the CESR storage ring operation in the center-of-mass energy range 3 - 5 GeV. Data taking could start as early as 2003. Estimates of the luminosity that a suitably modified CESR can deliver in this energy range imply data samples of 1 - 4 fb^-1 /year. The physics program of CLEO-c can be divided in two parts: weak interaction physics and QCD physics. Both programs will be presented and discussed.

Dans cette conférence, j'essaierai de faire une synthèse (incomplète) des développements dans quelques secteurs du domaine de l'astrophysique des particules. En particulier, je vais résumer les activités dans le domaine du rayonnement cosmique aux énergies les plus élevées, dans la recherche de sursauts de rayons gamma et des ondes gravitationnelles, et en cosmologie.

The Sudbury Neutrino Observatory is a 1 kilotonne D₂O Cerenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. Recent results confirming this hypothesis from 306 days of data will be presented. The analysis is based on observations of neutrinos from the decay of ⁸B via the charged current (CC) and Neutral Current (NC) reactions on deuterium and the elastic scattering (ES) of electrons above thresholds of 2.2 MeV (NC) and 5 MeV (CC and ES). This is the first direct measurement of the total flux of active ⁸B neutrinos arriving form the Sun. It is determined to be in good agreement with the predictions of solar models. The analysis will be discussed in the context of the Solar Neutrino Problem and the future science program at SNO will be presented, with mention of the challenging requirements of ultra-low levels of radioactivity.

A Photoinjector Test facility is in operation at DESY Zeuthen (PITZ) since end of 2001. The aim is to develop and operate an optimized photoinjector for future free electron lasers (FEL) and linear accelerators. In the first phase the energy of the produced electrons will reach about 5 MeV. A description of the photoinjector is given and first results will be presented as well as some special topics in the field of laser and electron beam diagnostics.
The PITZ facility in DESY Zeuthen is part of the preparation of the TESLA project. TESLA is the abbreviation for TeV Superconducting Linear Accelerator. This project consists of two main parts: The 30km long linear electron-positron collider and a X-ray Free Electron Laser (FEL). Both facilities will be described. The Tesla Test Facility (TTF) at DESY Hamburg is a running linac and FEL for the preparation of the TESLA project. In the last years remarkable results in the FEL research were obtained here.

The intrinsic tau neutrino flux produced in high energy cosmological and astrophysical sources has usually been considered negligible in comparison to the electron and muon neutrino fluxes. Also, the cascade tau neutrinos produced by the collisions of primary electron and muon neutrinos with the relic cosmic neutrino background is orders of magnitude less than the primary electron and muon neutrinos flux. Therefore, it is currently expected that any detected tau neutrino component from a source outside the Solar System to be indicative of neutrino oscillation. Our calculations show, however, that a tau neutrino flux component might be produced due to hadronic decays at the source. This tau neutrino component can considerably modify the expected intrinsic tau neutrino spectrum in many astrophysical and cosmological high energy neutrino production scenarios. As a consequence, the observation of a significant tau to muon neutrino ratio at a given energy in high energy neutrino telescopes and detectors may be due to hadronic decays at source and not muon to tau neutrino oscillation in transit.

We construct a star product associated with an arbitrary two dimensional Poisson structure using generalized coherent states on the complex plane. From our approach one easily recovers the star product for the fuzzy torus, and also one for the fuzzy sphere. For the latter we need to define the `fuzzy' stereographic projection to the plane and the fuzzy sphere integration measure, which in the commutative limit reduce to the usual formulae for the sphere.

The ADS/CFT correspondence asserts an exact duality between maximally supersymmetric Yang-Mills theory in four dimensions and type IIB superstring theory on the background AdS5XS5. Recently, it has been shown that one can obtain interacting string theory on a PP-wave background by taking a certain limit of AdS5XS5. Some features of the corresponding limit of super-Yang-Mills theory will be discussed.

We show how bosonisation coupled with renormalisation group analyses are useful tools in the study of real quantum (one-dimensional) wires. We use these methods to explain some recent experiments in quantum wires. We also study the fixed point behaviour when several quantum wires meet at a point, and make predictions for conductances, which can be experimentally tested.

It is a well- known phenomenon but nonetheless still remarkable: quantum fluctuations in the vacuum give rise to measurable physical manifestations, i.e. what is called the Casimir energy (or force). The classic example is that of two parallel conducting plates in vacuum attracting each other with a Casimir force proportional to 1/d4 where d is the plate separation. In this work, we obtain as a function of D the Casimir energy of the longitudinal (acoustic) modes of a relativistic perfect fluid confined to a hypercube with D spatial dimensions. Our results show that there exists a critical dimension D=36 for Dirichlet boundary conditions (field is zero on boundaries). For D36, the sign of the energy alternates: it is negative(attractive) when D is odd and positive(repulsive) when D is even. For D>36, the Dirichlet Casimir force is always attractive. For Neumann boundary conditions (derivative of field is zero) there is no critical dimension and the force is attractive for all D. Before starting directly with the general D-dimensional case, we illustrate our procedure with a simple one-dimensional object: the Bosonic string.

The spectrum of comic rays observed at Earth spans amazingly over 11 decades of energy. Although a wealth of data has been gathered during almost 100 years, there are still many unanswered questions about their origin, acceleration mechanism, and propagation. I will discuss these issues and talk about an even more intriguing set of questions that has been posed by the observation of the ultra high energy events.

Many inflating spacetimes are likely to violate the weak energy condition, a key assumption of many singularity theorems. In this talk I will describe a recent theorem by Vilenkin, Borde, and me which uses a simple kinematical argument, independent of any energy conditions, to show that a cosmological model that is inflating-- or just expanding sufficiently fast-- must be incomplete in null and timelike past directions. Specifically, we obtained a bound on the integral of the Hubble parameter over a past-directed timelike or null geodesic. Thus inflationary models require physics other than inflation to describe the past boundary of the inflating region of spacetime.

Remarkable progress has been made in both observational and theoretical cosmology, leading to the LCDM model, attributing 30% of the total Universe density to gravitational matter, and 70% to the so-called dark energy. About 1-2% of the matter is presently visible, the rest being composed of baryonic dark matter (DM), neutrinos and non-baryonic DM. The presence of neutralinos in halos around galaxies could solve the DM problem, and also support the SUSY extension of the Standard Model. Many detectors with extremely low backgrounds aim at its detection. One of these, the PICASSO Project, uses the technology of the bubble chamber. Substantial progress in the past year gives us confidence that this technique may lead to a detector with largely improved sensitivity to explore spin-dependent neutralino interaction. A new detector with increased mass is under construction for an experiment to be deployed in the underground laboratory of SNO.

The purpose of this talk is to present preliminary CLEO-III results on rare B two-body decay modes to final states including charged and neutral kaons and pions. The analysis uses 6 fb^-1 of CLEO-III data. An analysis of the mode B® K_sK_s using CLEO-II data will also be presented.

I will discuss the role of topological fluctuations (vortices) in the dynamics of the Abelian Higgs model in two spatial dimensions. I will describe how long lived clusters of like sign vortices appear in the cooling of type II materials (when the Higgs is heavier than the gauge field), and predict some of their properties. In type I (when the Higgs is light) I will show that vortices are intimatelly connected with the nucleation of the low temperature superconducting phase and that they undergo a clustering instability analogous to that of gravitational systems.
The Abelian Higgs model describes in some circumstances the long wave length behavior of superconductors. Some experimental signals of our results are discussed in this context.

All medical x-ray imaging today is done by using the primary or transmitted x rays to form a shadow picture of the patient. Up to 90% of the photons approaching the image receptor, however, have been coherently or incoherently scattered, and an alternative is to use them to generate the image. Thus, scattered radiation is no longer just a nuisance to be suppressed, but a new source of information. The underlying physics and basic approaches to scatter imaging will be presented. Results from the first systematic feasibility analysis to determine the sensitivity of the technique for different imaging geometries will be presented. Current work on measuring the basic cross sections will be summarized.

Les mesures de précision électrofaibles seront presentées: celles qui contraignent la masse du boson de Higgs, et celles qui testent precisément le Modèle Standard. Ces mesures seront placées dans le contexte des ajustements électrofaibles, qui permettent de prédire la masse du boson de Higgs (s'il existe). Ensuite, je parlerai des recherches directes du boson de Higgs SM, au LEP et au Tevatron. Je concluerai sur ce.

The historic observation of CP violation in the neutral B system at BaBar and BELLE this past year is just the first round in the systematic testing of the CP violating sector of the Standard Model. Through the study of rare B decays, one hopes to extract the three unitarity angles α, β and γ. The current BaBar and Belle results imply a non-zero value for β which will be greatly refined in the coming years. In this talk, I will discuss new ideas for the measurement of the more difficult parameters α and γ at B-factories. Although measuring these parameters will require more luminosity than is currently available, their determination is a key test of the Standard Model.

Lasers can be used to cool and trap neutral atoms. Such techniques won the 1997 Nobel Prize for Chu, Phillips, and Cohen-Tannoudji, and are revolutionizing a number of subfields of atomic physics. At TRIUMF, we are applying these techniques to a rather different problem, the study of nuclear beta decay. We use a Magneto-Optical Trap to capture beta-decaying nuclei and hold them suspended in space, free of any backing materials. By detecting the low-energy nuclear recoils in coincidence with the beta, we can reconstruct the neutrino momentum. The angular distribution of the neutrinos with respect to the beta direction is predicted by the Standard Model, and deviations from that prediction are sensitive to new interactions. We are also learning to use these atomic techniques to polarize nuclei to test whether parity is maximally violated in the charged weak interaction. Preliminary measurements of the beta-neutrino angular distribution from a spin-0 nucleus will be shown: our goal is to set limits on the existence of new scalar bosons complementary to those set by high-energy colliders.

I will review in short the recent developement on determination of weak phase gamma.

A brief introduction to the origin and detection of cosmic rays will be given. The Alberta Large Time Coincidence Array (ALTA) will then be described along with the potential physics case for such detector systems. The partnership between education at the highschool college and University level and fundamental research that the ALTA project has initiated will be discussed. Last but not least a sketch of the envisaged expansion of the ALTA project across North America -- the NALTA project (North American Large Time Coincidence Array) -- will be presented.

We argue that the evidence for nonzero neutrino masses is quite compelling. Then, we turn to the questions about neutrinos raised by the presence of their nonzero masses. These questions include: How many different neutrinos are there? How much do they weigh? Is each neutrino identical to its antiparticle? Does the behavior of neutrinos violate CP? How will we confirm the present evidence concerning neutrino masses, and then go on to answer questions like these?