Authors:	Baumholzer, Sven
Advisor:	Schwaller, Pedro
Title:	Searching for warm dark matter down on Earth and among the stars
Online publication date:	13-Apr-2022
Year of first publication:	2022
Language:	german
Abstract:	There are experimental and observational hints calling for new physics beyond the standard model (SM), among them the intriguing question of the nature of dark matter (DM). In this thesis we study the phenomenology of models featuring warm DM. First, we consider the scotogenic model, which features a radiative generation of neutrino masses, and explore its light dark matter phenomenology. In particular, we focus on keV-scale DM which can be produced either via a freeze-in mechanism through the decays of newly introduced scalars or the decays of the next-to-lightest fermionic particle in the spectrum. The latter possibility is required to be suppressed as it typically produces a hot DM component. Constraints from big bang nucleosynthesis (BBN) and the number of non-photonic relativistic particle species, N eff , are also considered, and in combination with couplings needed to produce enough DM, the DM candidate is required to be light. To estimate the discovery potential for this scenario we consider collider analyses at the high luminosity upgrade of the Large Hadron Collider (HL-LHC) and proposed future hadron and lepton colliders, namely FCC-hh and CLIC, focusing on final states with two leptons and missing transverse energy. Taking into account the cosmological bounds, we show that they already probe parts of the HL-LHC discovery region for this scenario, while future colliders access an even larger region of parameter space. Second, we derive structure formation limits on DM composed of keV-scale axion-like particles (ALPs), produced via freeze-in through their interaction with photons and SM fermions. We employ results from Lyman-α forest data sets as well as the observed number of Milky Way (MW) subhalos. We compare the momentum distribution function obtained using Maxwell-Boltzmann and quantum statistics for describing the SM thermal bath. It should be emphasized that the presence of logarithmic divergences complicates the calculation of the production rate. The results obtained in this way, in combination with gamma-ray bounds, exclude the possibility for a photophilic “frozen-in” ALP DM with mass below ∼ 19 keV. For the photophobic ALP scenario, in which DM couples primarily to SM fermions, the ALP DM distribution function is peaked at lower momentum and hence results in weaker limits on the DM mass. Future facilities, such as the upcoming Vera C. Rubin observatory, will significantly improve the current bounds up to ∼ 80 keV. Lastly, we generalize DM production via multiple mechanisms by introducing a model-independent framework and assess whether its consistency with structure formation observations. We simulate the matter power spectrum for DM scenarios characterized by at least two temperatures stemming from the different production mechanisms, and derive the suppression of structures at small scales and the expected number of MW subhalos. This allows us to obtain constraints on the parameter space of non-thermally produced DM. We propose a simple parameterization for non-thermal DM momentum distributions, present a fitting procedure that can be used to adapt our results to other models, and demonstrate via some toy models how our results can be applied to other non-thermal DM models.
DDC:	530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-6835
URN:	urn:nbn:de:hebis:77-openscience-c202a794-08c7-460e-9094-079db175559e9
Version:	Original work
Publication type:	Dissertation
License:	CC BY
Information on rights of use:	https://creativecommons.org/licenses/by/4.0/
Extent:	165 Seiten
Appears in collections:	JGU-Publikationen