Particle Physics

The Standard Model is currently the theory which describes the most fundamental constituents of matter and the forces which govern their interactions. Since the start-up of the LHC accelerator, the ATLAS detector has collected sufficient data to allow tests of this theory at the smallest distance scales ever probed. The objective is to find significant deviations between the observed data and the Standard Model predictions, revealing the existence of new phenomena. For example, some theories in which the universe has more than 4 space-time dimensions predict that LHC collisions could produce gravitons - the particles responsible for the gravitational interaction. Such events would feature a single jet of hadronic particles in the detector and a large amount of

We propose models of symmetric WIMP dark matter in which dark matter annihilations generate the baryon asymmetry. We call this mechanism "WIMPy baryogenesis". This provides a dynamical connection between the late-time abundances of both dark matter and baryons. We construct explicit models of leptogenesis and baryogenesis at the weak scale, and find the "miraculous" result that, for order one couplings and weak scale masses for any new fields, the baryon asymmetry and dark matter relic density from WIMPy baryogenesis match the observed values. We also discuss implications for the LHC and dark matter detection experiments.

The LHC has just concluded this year's proton-proton run at 7 TeV CM energy, producing more than 5fb-1of data. While the full data sample collected by the CMS experiment will be analyzed over the winter, many of the present searches for new physics have been completed with 1-2 fb-1. In this talk we will present the most recent updates on the search analyses in CMS, including the Higgs search, searches for supersymmetry, and a plethora of other BSM models, such as extra dimensions, Z's, W_R, leptoquarks, and more. We'll also show the short-term and longer-term plans of the collider and experiments.

The Enriched Xenon Observatory (EXO) collaboration has observed the two-neutrino double beta decay of 136Xe with EXO-200, a prototype to the full EXO detector in development. This second order process, predicted by the Standard Model, has been observed for several nuclei but not for 136Xe. The observed decay rate provides new input to matrix element calculations and to the search for the more interesting neutrino-less double-beta decay, the most sensitive probe for the existence of Majorana particles and the measurement of the neutrino mass scale. The motivation to search for neutrino-less double-beta decay will be discussed. An overview of experimental efforts, and the status of calculations of nuclear matrix elements will be given. The EXO-200 detector and underground site at WIPP, New Mexico, will be presented, and the observation of the two-neutrino decay discussed. The presentation will then focus on the development of EXO Full, a multi-tonne detector with the ability to identify the daugther ion as a powerful background reduction tool, with SNOLAB a possible site.

In this talk, I will discuss constraints on dark matter (DM) from collider physics, neutron stars and DM halo shapes. Monojet plus missing energy searches at hardron colliders limit DM interactions with quarks and gluons, which provide a complementary probes of DM to direct detection. Stars can capture ambient DM particles. The captured scalar DM particles may form a Bose-Einstein condensate, leading to a black hole at the center of the host neutron star that eventually causes its destruction. The observation of old neutron stars exclude a wide range of the DM-neutron scattering cross-section for the scalar asymmetric DM. In various well-motivated models, DM has self-interactions which may leave imprints on galactic dynamics. I will discuss an upper bound on DM self-interaction cross section derived from elliptical DM halo shapes which is about two orders of magnitude stronger than the result from the Bullet Cluster.