Weighing the Gravitophobic Neutrinos
Robert Ehrlich · 2022
Weighing the neutrino has been a long-time goal of particle physics that has proven to be exceptionally difficult, given the smallness of their masses. Of the three neutrino flavors, the muon neutrino mass can be found in principle by looking at single events in which a pion decays, but for the electron neutrino a statistical distribution of events is needed. The shape of the beta decay spectrum near the endpoint can reveal the electron neutrino mass. Earlier (pre-KATRIN) beta decay experiments done by various groups only were able to set upper limits on the mass, and the most accurate ones before KATRIN by the Mainz and Troitsk groups lowered the upper limit to 2 eV. Those earlier experiments assumed the three neutrino masses have nearly equal values, based on the standard neutrino model, so that only a single effective mass for the electron neutrino (or antineutrino) can be used. Those earlier experiments, however, also fit the author’s 3 + 3 model (including a tachyon) just as well as they do a single mass of 2 eV or less. The more sensitive KATRIN experiment should resolve this ambiguity once it has taken enough data.