High Energy Physics

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 present a first principle construction of a holographic dual for gauged matrix models. The dual theory is a closed string field theory coupled with an emergent two-form gauge field defined in one higher dimensional space. The bulk space with an extra dimension emerges as a well defined classical background only when the two-form gauge field is in the deconfinement phase. Based on this, it is shown that critical phases that admit holographic descriptions form a novel universality class with a non-trivial quantum order.

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.