High Energy Physics

DEAP-3600 is a dark matter experiment using 3600 kg of liquid argon for direct WIMP search, with a target sensitivity to the spin-independent WIMP-nucleon cross-section of 10^{-46} cm^2. The detector is currently under construction at SNOLAB, located 2 km underground in Sudbury. In this single-phase liquid argon experiment, discrimination of beta/gamma backgrounds from the WIMP-induced nuclear recoil signal will be achieved by analyzing the pulse shape of scintillation light. A prototype 7-kg liquid argon detector has been taking data at SNOLAB since 2007 and has allowed extensive background studies, including significant radon and surface contamination reduction. The status of the experiment and of background reduction studies will be presented.

We describe a model of composite dark matter, bound by an asymptotically free gauge interaction. This leads to a novel relic history and to an enhancement of the present-day dark matter annihilation cross section. Potential indirect detection signals are discussed.

Many explanations have been proposed for the origin of dark matter and the creation of the baryon asymmetry, but very few of them address both cosmological puzzles at once. At the same time, the observed energy densities of dark matter and baryons are within a factor of five of each other hinting at a possible common origin. In this talk I will present a novel mechanism that generates both densities at once, with the dark matter species carrying a net baryon number. This gives rise to new and unusual dark matter signals such as the destruction of nucleons by dark matter scattering. I will describe some of these signals, and discuss how they might be detected in current and upcoming experiments and astrophysical observations.

I discuss the challenges for building models of ~10 GeV dark matter that can accommodate the numerous astrophysical constraints that threaten to exclude them, as well as direct detection constraints. A U(1)xU(1) hidden sector model with isospin violation, inelastic couplings, and annihilation into invisible products is suggested. I will also discuss similar but simpler models that could simultaneously explain excess 511 keV gamma rays from the galactic center and direct detection of light dark matter.

Stability on cosmological time scales constitutes one of the few robust guiding principles in the formulation of a theory of dark matter. This suggests the existence of a stabilizing symmetry associated to dark matter. I will explore several examples of stabilizing symmetries beyond the canonical Z_2 parity, such as Abelian Z_N discrete gauge symmetries, Non-Abelian discrete symmetries, and flavor symmetries.

In my talk I will discuss the relevant astrophysical input for dark matter detection experiments, i.e. the expected distribution of dark matter at the solar position. Based on high resolution N-body simulations I will then show that the formation history of the galactic dark matter halo leaves imprints in the velocity and energy distribution. In the second part of my talk I will focus on the fine-grained dark matter structure and discuss the importance of caustics and streams for detection experiments.

High resolution simulations of Galactic Cold Dark Matter halos reveal staggering amounts of substructure, both in configuration and velocity space. In this talk I will focus on the latter. In addition to spatially localized subhalos and streams, I will also discuss so-called debris flows -- incompletely phase-mixed material originating in numerous accretion and merging events that are the hallmark of the hierarchical build-up of the host halo. Finally, I will briefly discuss the presence and direct detection consequences of a dark disk in the Eris simulation, a cosmological simulation including baryonic physics of the formation of a realistic looking disk galaxy.

The simplest singlet Higgs-portal dark matter model predicts large/dominant Higgs ->2 DM decay widths in the region of parameter space with m_DM < m_h/2, and Higgs mass below 140 GeV. On the other hand, the direct detection experiments such as Xenon100 put stringent constraints on the scattering DM-nucleon scattering cross section and seemingly exclude large part of the parameter space where the invisible Higgs decay dominates over visible modes. I analyze the robustness of this statement in the next-to-minimal models to show that the relation between invisible Higgs width and dark matter cross section does not hold in general. I discuss a number of theoretical scenarios where WIMP abundance is regulated by the Higgs portal, the direct detection signals are small AND Higgs decay width is dominated by the decay to dark matter.

We analyze the recently released CoGeNT data with a focus on their time-dependent properties. Using various statistical techniques, we confirm the presence of modulation in the data, and find a significant component at high (Eee \gtap 1.5 keVee) energies. We find that standard elastic WIMPs in a Maxwellian halo do not provide a good description of the modulation. We consider the possibility of non-standard halos, using halo independent techniques, and find a good agreement with the DAMA modulation for QNa