Sterile Neutrino Search with the KATRIN Experiment

Abstract

The KATRIN experiment is the most precise setup for direct neutrino mass measurements. It is designed and optimised to measure the signature of the neutrino mass in the β-decay spectrum of tritium with a sensitivity of 0.2 eV/c 2 (90 % C.L.) [7]. In addition to the neutrino mass search, the measured β-spectrum can be analysed for an imprint of sterile neutrinos in the eV-range. The first and second KATRIN science runs were taken in 2019. Between these two campaigns, the source activity was substantially increased, leading to improved constraints. No sterile-neutrino signal was observed in the mass range up to 40 eV, and the exclusion contours improved, constraining the active-to-sterile mixing to |𝑈 𝑒4 | 2 < 6 × 10 −3 (95 % C.L.) [2]. With analysis deeper into the spectrum, it is also possible to search for keV-scale sterile neutrinos. During the commissioning phase in 2018, a low source density allowed the opportunity to search for sterile neutrino masses up to 1.6 keV. From this data, mixing amplitudes of |𝑈 𝑒4 | 2 < 5 × 10 −4 (95 % C.L.) are excluded. No sterile neutrino signature was found in the keV-range [3].8th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE 2022