Session J1: Dark Matter and Dark Energy

The Dark Energy Survey

I will introduce the Dark Energy Survey, highlighting some of our most recent results, and touching on some of the exciting science that is coming down the line.   

Ultrasensitive Phonon-Mediated Detectors for Dark Matter Searches

Astrophysical observations indicate that over 80\% of the mass in the Universe is made of nonbaryonic, dark matter. Further measurements have shown that the most likely candidates for this matter are exotic, as yet undiscovered, particles that only interact weakly with ordinary matter. Experiments such as the SuperCDMS (Cryogenic Dark Matter Search) have been pioneers in the effort to detect these elusive particles. However, the lack of experimental evidence for high-mass dark matter particles combined with the recent emergence of theoretical models that favor low-mass dark matter underscores the need to develop detectors with low energy threshold capability to probe these low masses. One approach to address this is to use Luke-Neganov amplification to measure phonons produced during nuclear recoils in high-purity semiconductor detectors to very high precision. I will outline this approach and how it applies to CDMS high-purity semiconductor detectors and summarize recent developments in this field, including steps to address the leakage current that is its main limiting factor.   

Dark Matter and Neutron Stars

Compact Stars near the center of the Galaxy are thought to be in the presence of a significant density of dark matter (DM). Based on the particle model of DM, a wide variety of global and local effects can be seen in the stars. After a significant number of DM particles are bound to the star via gravitational, nucleon-DM, and DM self interactions, effects can be seen in the temperature, lifetime, and equation of state (EoS) of the star. Results are presented for constraints on the DM parameter space that allows for gravitational collapse of the star. Different models for particle DM are tested and the effect on the bulk properties and EoS of compact nuclear matter are presented.   

A Razor Search for Dark Matter at a Future 100 TeV Collider

The existence and nature of dark matter is one of the most exciting (and perplexing) issues in modern physics. The Minimal Supersymmetric Standard Model provides a viable candidate for dark matter in the form of the lightest supersymmetric particle (LSP), which is predicted to be absolutely stable. We can study such particles at high energy colliders. The potential for studying supersymmetric dark matter and related particles at the Large Hadron Collider, with a center of mass energy of 14 TeV, however, is very limited. The recently proposed 100 TeV proton proton collider would open up many opportunities to find new physics. In this talk, I will describe a search strategy for Higgsinos (the superpartners of the Higgs boson) that decay to pure bino LSP dark matter at a 100 TeV proton-proton collider using 'razor' kinematical variables, and show what regions of the MSSM parameter space it can probe.   

Intra-Ensemble Decays in Non-Minimal Models of the Dark Sector

In non-minimal models of the dark sector such as Dynamical Dark Matter (DDM), the dark-matter candidate consists of a vast ensemble of particles with different masses, mixings, and cosmological abundances. In general, the ensemble is organized in such a way that components decaying earlier are less abundant than components decaying later. However, most previous work on DDM assumes that the intra-ensemble decays of dark-matter particles are negligible compared to decays directly to the Standard Model. While in many cases this is indeed true, there exist cases for which intra-ensemble decays cannot be ignored and have important effects. In this work, we study the intra-ensemble decays of a DDM ensemble consisting of an infinite tower of Kaluza-Klein (KK) states subject to a cubic interaction. Boltzmann equations are used to show the evolution of the distribution functions and the collective equation of state for the ensemble as a whole.