An enquiry into dark matter physicsRai, Mudit (2023) An enquiry into dark matter physics. Doctoral Dissertation, University of Pittsburgh. (Unpublished) This is the latest version of this item.
AbstractThis thesis aims to address some of the issues plaguing the Standard Model of particle physics and cosmology, with a particular focus on new theoretical and phenomenological approaches to the dark matter puzzle. First we perform an in-depth phenomenological analysis of the potential observable consequences of the Higgs and neutrino portal dark sector models at the Fermilab DarkQuest proton beam fixed-target experiment. Our findings show that DarkQuest will have excellent sensitivity to new weakly coupled scalars and fermions in the GeV-scale mass range. Next, we construct and investigate renormalizable models of Flavor-Specific Scalar mediators, which dominantly couple with a certain specific fermion mass eigenstate. This work opens a pathway for new dark sector theories with novel flavor structures and distinctive phenomenology. We also investigate the cosmological production of ultra-light scalar dark matter with a feeble coupling to the Higgs field where we analyzed the effects of the SM thermal bath and the electroweak phase transition on the late time relic abundance. Our results include new relic density targets which can be compared with experimental and observational tests. In a complementary direction,we also study several foundational questions in early universe cosmology, which, in addition to their instrinsic theoretical interest, can also provide an altogether different framework for understanding dark matter. Firstly, we study the emergence of entropy in the gravitational production of ultralight dark matter particles. Thereafter, we investigate the transition rates and cross sections for two-to-two scattering processes in a spatially flat radiation dominated cosmology. We then focus on the infrared dressing of bosonic or fermionic heavy particles by a cloud of (nearly) massless particles, which can lead to a unique production mechanism of ultralight dark matter or dark radiation in a radiation-dominated cosmology. We find that the initial amplitude of the single particle decays in time with a power law behaviour, instead of the usual exponential decay of the asymptotic Minkowski spacetime. Share
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