Statistical criteria for search of heavy neutrino in tritium spectrum

The method of quasi-optimal weights is applied to constructing (quasi-)optimal criteria for search of heavy (4th generation) neutrino contribution in experimental β-decay spectra. Various approaches to searching for anomalous contributions in spectra are discussed. In particular the tritium β-decay spectrum (for instance, in Troitsk-v-mass, Mainz Neutrino Mass and KATRIN experiments) is analyzed using the derived special criteria. The power functions constructed for each criteria show the efficiency of the derived quasi-optimal criteria as statistical instruments for detecting the anomalous contributions in the spectra. The overall sensitivity of the criteria is estimated.