Presentation of master thesis in physics. The title of the master thesis is "Direct detection limits on general spin-0, spin-½, and spin-1 dark matter - electron interactions".
Inconsistencies in observations, ranging from sub galactic scale to the largest scale currently possible to probe, suggests the existence of unseen mass which does not appear to interact with electromagnetic waves of any wavelength, which in the current paradigm is hypothesised to consist of so far undetected particles. Modern cosmology predicts that the known visible mass only contributes to 5% of the total mass-energy of universe, with Dark Matter (DM) 27% and Dark Energy the remaining 68%.
One promising method for detecting DM particles is direct detection experiments, performed in low background environments deep underground. For decades direct detection experiments have been carried out in hopes of detecting DM induced nuclear recoil events. During this the leading DM model has been the Weakly Interacting Massive Particle (WIMP) model in which the DM mass in general was in the same order as the nucleus mass. However due to the lack of results from the nuclear recoil experiments alternative models started being investigated. One such class of models are the simplified models for light DM, which extends the Standard Model (SM) by one single DM-WIMP and one single mediator which couples the DM to the SM particles. In such simplified models the DM mass can be too small to cause nuclear recoil and interactions with ordinary matter instead primarily occurs via electrons.
In this work we present a general framework before applying it to six general simplified models, including spin-0, spin-½ and spin-1 DM, then in the context of direct detection, presents the DM induced electron transition rates in silicon and germanium crystals and finally calculate 90% confidence level exclusion limits on the interaction strength based on the data from direct detection experiments using silicon and germanium detectors.
Interactions between spin-1 DM and electrons has previously not been fully investigated, leading now to a unified interpretation of spin-0, spin-½ and spin-1 DM models.