Probing the neutrino mass with tritium beta decay

by Kathrin Valerius (KIT Karlsruhe)


Precision measurements of the kinematics of weak decays offer a direct and nearly model-independent approach to probe the absolute neutrino mass scale. The KArlsruhe TRItium Neutrino experiment (KATRIN) is searching for the minute imprint of the neutrino mass in the endpoint region of the tritium beta-decay spectrum. KATRIN employs a high-intensity gaseous molecular tritium source and a high-resolution electrostatic filter with magnetic adiabatic collimation to target a neutrino-mass sensitivity of 0.2eV/c^2, thus improving on previous experiments by an order of magnitude, after five years of data-taking.

With just its first science run, KATRIN has improved previous direct neutrino mass bounds by about a factor of two, yielding a new upper limit of 1.1 eV/c^(90% CL), and has begun to address further science channels such as the direct search for light sterile neutrinos. As larger data sets are collected and further improvements in terms of signal-to-background ratio and systematics are being achieved, KATRIN is continuing along its path towards sub-eV neutrino mass sensitivity and the exploration of interesting BSM physics cases. 

[1]  KATRIN Collaboration, “Improved upper limit on the neutrino mass from a direct kinematic method by KATRIN”PRL 123 (2019) 221802
[2] KATRIN Collaboration, Bound on 3+1 Active-Sterile Neutrino Mixing from the First Four-Week Science Run of KATRINPRL 126 (2021) 091803
[3] KATRIN Collaboration, Analysis methods for the first KATRIN neutrino-mass measurement“arXiv:2101.05253