SDD prototypes with the IDef-X readout for the keV-scale sterile neutrino search with TRISTAN and analysis of first tritium data

Sterile neutrinos are hypothetical leptons that are not included in the Standard Model of particle physics (SM). Several theories introduce sterile neutrinos as right-handed fermions within a minimal extension of the SM. These neutrinos would not take part in the weak interaction but would mix with active neutrinos. Despite overwhelming cosmological and observational evidence for the existence of dark matter its nature is still unknown. A sterile neutrino with a mass & 1 keV is a candidate particle (arXiv:1602.04816). Such a neutrino could be discovered in a laboratory by observing the signature of the heavy mass-eigenstate mixing in beta spectra with the TRISTAN project. TRISTAN is an expansion of the KATRIN experiment. KATRIN examines the end point of the tritium spectrum to measure the neutrino mass by counting electrons that pass a threshold, which is applied by an electromagnetic filter (MAC-E filter), thus measuring an integral spectrum. For the TRISTAN project (phase 1) KATRIN will be equipped with a novel 3000-pixel silicon drift detector (SDD) array that can handle high rates such that the entire tritium spectrum can be scanned.