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 Title: Dark matter phenomenology and model-building Author(s): Gaidau, Cristian Director of Research: Shelton, Jessie Doctoral Committee Chair(s): El-Khadra, Aida X Doctoral Committee Member(s): Neubauer, Mark; Filippini, Jeffrey P Department / Program: Physics Discipline: Physics Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): dark matter theoretical physics beyond standard model astroparticle physics indirect detection of dark matter self-interacting dark matter Abstract: The nature of dark matter is one of the biggest outstanding mysteries in particle physics. Cosmological observations firmly establish the existence of dark matter via its gravitational effects. On the other hand, the particle nature, origin and non-gravitational interactions of dark matter remain unknown. In this thesis, we present a collection of efforts aimed at studying the dark matter problem from two directions. The first direction is the construction of well motivated particle models for dark matter, which simultaneously offer novel experimental and observational signatures while extending the theoretical model space for the origin and evolution of dark matter. The second direction is using the cosmos and astrophysical objects as laboratories which can constrain the properties of dark matter. In Chapter 2 we construct a method for probing the strength of dark matter self-interactions, which is based on dark matter indirect detection signatures in the solar system. The dominant effect of self-interactions in the Sun is to provide an additional channel for capture, while the dominant effect in the Earth is to eject previously captured dark matter. We compute the annihilation fluxes of Sun and Earth captured dark matter and describe how the existence of dark matter self-interactions can be deduced by comparing the annihilation rates of dark matter gravitationally bound within the Sun and Earth. The solar system test described above is constructed for short-range dark matter self-interactions and dark matter-nucleus interactions. In Chapter 3 we revisit the gravitational capture problem for long-range interactions. We demonstrate that neglecting the thermal motion of target particles, which is a good approximation for short-range interactions, is no longer justified for long-range interactions. We find that restoring the thermal motion of target particles changes the functional dependence on model parameters and greatly magnifies the rate of dark matter capture. In Chapter 4 we introduce leak-in dark matter, a novel out-of-equilibrium origin for the dark matter in the universe. We provide a comprehensive and unified discussion of a minimal, internally-thermalized, hidden sector populated from an out-of-equilibrium, feeble connection to the hotter standard model sector. We emphasize that when this out-of-equilibrium interaction is renormalizable, the colder sector undergoes an extended phase of non-adiabatic evolution largely independent of initial conditions, which we dub leak-in". We discuss the leak-in phase in generality, and establish the general properties of dark matter that freezes out from a radiation bath undergoing such a leak-in phase. Issue Date: 2021-09-20 Type: Thesis URI: http://hdl.handle.net/2142/113809 Rights Information: Copyright 2021 Cristian Gaidau Date Available in IDEALS: 2022-04-29 Date Deposited: 2021-12
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