Direct Neutrino Mass Experiments and Exotic Charged Current Interactions
  We study the effect of exotic charged current interactions on the electron energy spectrum in tritium decay, focussing on the KATRIN experiment and a possible modified setup that has access to the full spectrum. Both sub-eV and keV neutrino masses are considered. We perform a fully relativistic calculation and take all possible new interactions into account, demonstrating the possible sizable distortions in the energy spectrum. 
Patrick Otto Ludl, Werner Rodejohann
hep-ph hep-ex nucl-ex nucl-th