Dark Matter and Neutrinos: A Love-Hate Relationship

Abstract

Dark matter (DM) and neutrinos provide the two most compelling pieces of evidence for new physics beyond the Standard Model (SM) but they are often treated as two different sectors. A tantalising avenue of
investigation is the possibility that a stronger connection between these two particles
exists. In this thesis, we explore the phenomenological implications of a neutrino-DM coupling and show that the complementarity between cosmological observables and indirect detection searches can be used to exclude large regions of the parameter space for different DM models. After conducting a complete study of all the possible renormalizable scenarios with such a coupling, we discuss two gauge-invariant realisations of models where the DM phenomenology is dominated by its interactions with neutrinos. While in these models, neutrinos set the strongest constraints, they can also be an obstacle in our quest to understand DM. Indeed, they will soon become a source of an important background for direct detection experiments. Here, we also compute the changes in this background in the presence of new physics within the neutrino sector. We find that it can increase significantly for light DM masses. This means that future discovery claims by direct detection experiments must be carefully examined if a signal is found well above the expected SM neutrino background.