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Particle Physics

This series consists of talks in the areas of Particle Physics, High Energy Physics & Quantum Field Theory.

Seminar Series Events/Videos

Currently there are no upcoming talks in this series.

 

Mardi mai 29, 2012
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Precision timepieces are marvels of human ingenuity. Over the past half-a-century, precision time-keeping has been carried out with atomic clocks. I will review a novel and rapidly developing class of atomic clocks, optical lattice clocks. At their projected accuracy level, these would neither lose nor gain a fraction of a second over estimated age of the Universe. In other words, if someone were to build such a clock at the Big Bang and if such a timepiece were to survive the 14 billion years, the clock would be off by no more than a mere second.

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Mardi mai 22, 2012
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A beautiful understanding of the smallness of the neutrino masses may be obtained via the seesaw mechanism, whereby one takes advantage of the key qualitative distinction between the neutrinos and the other fermions: right-handed neutrinos are gauge singlets, and may therefore have large Majorana masses. The standard seesaw mechanism, however, does not address the apparent lack of hierarchy in the neutrino masses compared to the quarks and charged leptons, nor the large leptonic mixing angles compared to the small angles of the CKM matrix.

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Mardi avr 24, 2012
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The IceCube neutrino observatory is the world's largest high-energy neutrino telescope, utilizing the deep Antarctic ice as the Cherenkov detector medium.  In December 2010 the last of the observatory's 86 strings of optical detectors was deployed, completing the approximate cubic-kilometer array.   With the addition of a low-energy extension, called DeepCore, the observatory has very high neutrino detection efficiency for energies ranging from ~10 GeV to a few EeV.  The low-energy threshold establishes the first steps towards precision neutrino measurements in the Antarctic.

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Mardi avr 17, 2012
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Direct dark matter (DM) detection experiments almost always focus on Weakly Interacting Massive Particles (WIMPs), which have a mass in the 1--1000 GeV range.  However, what if DM is not a WIMP?  In this talk, new direct detection strategies for DM particles with MeV to GeV mass will be presented.  In this largely unexplored mass range, DM can scatter with electrons, causing ionization of atoms in a detector target material and leading to single- or few-electron events.  I will present the first direct detection limits on DM as light as a few MeV, using XENON10 data.

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Mardi avr 10, 2012
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During the last ten years, a lot of experimental information has been collected from neutrino oscillation experiments  on the masses and and mixings among the three known  neutrino species. This presents  an almost comparable flavor picture for leptons as is already known to exist for quarks. In the talk I would like to discuss what these results imply for physics beyond the standard model since SM predicts zero neutrino mass.

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Mardi mar 27, 2012
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Models with right-handed currents have recently attracted attention because of their potential ability to solve the discrepancy in various determinations of |V_{ub}|. We consider a minimal setup with an SU(2)_L x SU(2)_R x U(1)_{B-L} gauge symmetry, for which we perform a simultaneous analysis of the most important constraints from electroweak precision observables, particle anti-particle mixing and the B -> X_{s,d} gamma decays.

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Mardi mar 20, 2012
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The axion provides a solution to the strong CP problem and is a cold dark matter candidate.  I'll briefly review the limits on the axion from particle physics, stellar evolution and cosmology.  The various constraints suggest that the axion mass is in the micro-eV to milli-eV range.  In this window, axions contribute significantly to the energy density of the universe in the form of cold dark matter.  It was recently found that dark matter axions thermalize and form a Bose-Einstein condensate (BEC).  As a result, it may be possible to distinguish axions from other forms of dark matter, suc

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Vendredi mar 09, 2012
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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.

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Vendredi mar 09, 2012
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The Large Hadron Collider has been operating for more than a year and delivering exciting results. It has already excluded large parts of the parameter space for supersymmetry. If the hints of a Higgs boson at 125 GeV hold up, the implications for supersymmetry are even more profound. I will explain some of the consequences, including the failure of large classes of models like general gauge mediation to account for such a heavy Higgs.

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Jeudi mar 08, 2012
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The LHC is offering our first glimpses of physics at energies above a TeV, allowing us an unprecedented chance to search for very heavy new particles from electroweak compositeness, new gauge forces, extra dimensions, and supersymmetry.  Some of the most interesting signals involve decays into Standard Model particles that we are used to thinking of as "heavy":  W/Z bosons, top quarks, and perhaps Higgs bosons.  However, at genuinely TeV-scale energies, these SM particles with O(100 GeV) mass are produced with relativistic velocities.  Consequently, their own decay products are Lorentz-boo

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