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T: Fachverband Teilchenphysik

T 81: Neutrinophysik 7 (Doppelbetazerfall, sterile Neutrinos)

T 81.7: Vortrag

Mittwoch, 29. März 2017, 18:25–18:40, VSH 118

Backscattering on the KATRIN rear wall as a systematic effect for a keV sterile neutrino search — •Ellen Förstner for the KATRIN collaboration — KIT

The main goal of the KArlsruher TRitium Neutrino experiment (KATRIN) is the determination of the effective electron anti-neutrino mass. The TRISTAN project of KATRIN focuses on a possible upgrade of KATRIN that would allow the search for sterile neutrinos up to the keV mass range. A keV-scale sterile neutrino would imprint itself as a kink-like distortion of the tritium beta decay spectrum. This signature is extremely small and therefore a very precise understanding of the theoretical and experimental systematic effects is necessary.

One systematic effect is caused by backscattering of beta-decay electrons on the gold rear wall of the KATRIN-setup. Backscattering of electrons causes an energy and angle change and hence significantly distorts the tritium beta decay spectrum.

The effect can be mitigated by the following countermeasures: 1) reduced magnetic field at the rear wall, 2) low-Z rear wall materials, 3) reduced tritium source strength. Using Kassiopeia and Geant4 Monte-Carlo simulations the influence of the rear wall on a keV-scale sterile neutrino search with KATRIN has been investigated and an optimized rear wall design has been developed. In this talk, the systematic effects related to the rear wall and the new mitigation techniques will be presented.

This work has been supported by BMBF (05A14VK2), KSETA and the Helmholtz Association.