Number 50 (Story #3), October 3, 1991 by Phillip F. Schewe and Ben Stein THE TAU NEUTRINO MASS must be less than 35 MeV, according to scientists using the ARGUS detector at the DESY electron-positron collider in Hamburg. One hears about the search for neutrino mass, but that usually refers to the electron neutrino or muon neutrino. The tau (a heavy cousin of electrons and muons) and its associated neutrino are harder to produce and hence harder to study. Besides putting a limit on the tau neutrino's mass, the ARGUS group also measured its helicity; like the other neutrinos, the tau neutrino is left-handed. That is, the spin of the tau neutrino points in a direction opposite to its direction of motion. (CERN Courier, Sept. 1991.)