Thesis defense of Dominik Döring

In this thesis, we study two dierent Standard Model extensions involving neutral leptons aiming to explain current anomalies in the neutrino sector, as well as to explain the avor anomalies in combination with the dark matter abundance in the universe. At rst, we develop a model that introduces additional sterile neutrino states featuring altered dispersion relations in order to explain the longstanding short baseline neutrino oscillation anomalies and the gallium/reactor anomalies, while also staying in accordance with high energy data from atmospheric and long baseline accelerator experiments. Furthermore, we systematically analyze a model class of oneloop solutions to the B-anomalies in the context of fermionic singlet dark matter candidates. We study the dark matter phenomenology for both Dirac and Majorana fermions in all ve models that contain a fermionic singlet. In our analysis, we include dierent hierarchies between the new Yukawa couplings to Standard Model quarks and also examine dierent mass ratios in the dark sector. Our study shows that especially direct detection limits can probe such solutions
of the B-anomalies.