Speaker
Description
In this talk I will show how to leverage cosmological data sets to search for new light–but not necessarily massless–degrees of freedom. These light relics arise ubiquitous in BSM theories, and their feeble interactions with the visible sector make them decouple in the early universe, and thus conserve significant number densities. Due to their small couplings, and large cosmic abundances, these BSM degrees of freedom are most powerfully searched with cosmological datasets. Massless relics act as a simple change in the number N_eff of effective neutrinos. Light but Massive Relics (LiMRs), however, also affect the clustering of matter, in a manner similar to that of massive neutrinos. I will show how current CMB+LSS data covers a large part of the relic parameter space, and in particular how they set the tightest constraints on the gravitino mass at 3 eV (95% CL).
