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An enquiry into dark matter physics

Rai, Mudit (2023) An enquiry into dark matter physics. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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This 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.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Rai, Muditmur4@pitt.edumur40000-0003-2876-809X
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBatell,
Committee MemberBoyanovsky,
Committee MemberZentner,
Committee MemberBoudreau,
Committee MemberMorningstar,
Date: 11 May 2023
Date Type: Publication
Defense Date: 5 April 2023
Approval Date: 11 May 2023
Submission Date: 22 March 2023
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 320
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Physics
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: None
Date Deposited: 11 May 2023 13:47
Last Modified: 11 May 2023 13:47

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