Phenomenological Explorations in Dark Matter

Abstract

The previous decade has seen an explosive increase in explorations into the nature of dark matter (DM) encompassing astrophysical, particle and cosmological probes. We face today a large body of gravitational evidences supporting the existence of dark matter and yet must grapple with ambiguity about its particle nature. This makes it one of the most important and challenging questions in physics, with a wide range of implications. Of particular interest is the interplay between the particle nature of dark matter and its astrophysical and cosmological manifestations. In this thesis, we address a few important questions regarding the possible properties of dark matter. The thesis consists of two parts. The first part explores lepton flavored dark matter (LFDM). One of the main results of this part is the connection between the stability of dark matter and the symmetries it possesses. We systematically show that many representations of lepton flavored dark matter are stable under the minimal flavor violation (MFV) hypothesis as long as there are no lepton number violating interactions. As a special case of the stability condition, we show that DM carrying certain charges under lepton number are trivially stable from lepton number conservation alone. We then study the cases of freeze-in mechanisms for relic density production and their detection phenomenology. We see that the LFDM in the MFV framework naturally accommodates a freeze-in production. Additionally, the notoriously difficult to detect freeze-in mechanism leads to some observable signatures at present and future direct detection experiments in minimal models of LFDM. In the second part of the thesis, we explore two important questions related to direct and indirect searches for dark matter. The latest results from the direct detection experiment XENON1T achieved unprecedentedly low background rates in electron recoil events for O(keV) recoil energies, with the future experiment XENONnT projected to lower it even further. Motivated by this,...