The KArlsruhe TRItium Neutrino experiment (KATRIN) is performing a high precision spectroscopy of the tritium beta-decay spectrum to search for the signature of the neutrino mass. It combines a high-intensity gaseous molecular tritium source and a high-resolution electrostatic spectrometer with magnetic adiabatic collimation. This allows KATRIN to reach a sub-eV sensitivity to the neutrino mass. Moreover, existence of the fourth neutrino-mass eigenstate (sterile neutrino), a new light boson and exotic general weak interactions are investigated. The analysis of the first five KATRIN measurement campaigns results in a new neutrino-mass upper limit m_<0. 45 \, eV at 90% confidence level (CL) and the existence of a sterile neutrino is excluded in the studied region with 95% CL. In the analysis of the second measurement campaign we derive competitive constrains on general neutrino interactions and evaluate the campaign's sensitivity to the existence of the new light bosons.
J. Štorek (Tue,) studied this question.