Relativistic Evolution of Dark Matter

Mondal, Rajrupa (2023) Relativistic Evolution of Dark Matter. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Rajrupa Mondal (18MS099)) Thesis_18MS099.pdf - Submitted Version Restricted to Repository staff only Download (1MB)

Abstract

Historically in dark matter studies, a non-relativistic freeze-out of dark matter particles has often been assumed. In such cases, the Maxwell-Boltzmann statistics are used to describe the equilibrium phase space distribution of the particle. However, this assumption does not hold in general non-WIMP models, where freeze-out can take place at relativistic momenta. This necessitates the addition of full quantum statistics, in the form of Fermi-Dirac or Bose-Einstein distributions, wherever applicable. The goal of the thesis is to account for quantum statistical effects in a simple extension of the Standard Model. It includes a fermion ν as a dark matter candidate and an unstable scalar s. The number density of ν is controlled by a 2 → 2 process where the fermion annihilates into the dark scalars and freeze out can occur in the relativistic regime. The thesis analyzes the corresponding relativistic reaction rate based on the Fermi-Dirac and Bose-Einstein distributions.

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