Limits on the Mass of the Tau Neutrino from CLEO

Abstract

A limit on the mass of the tau neutrino is derived from 4.5x10^6 tau pairs produced at a center of mass energy of 10.6 GeV. The measurement technique involves a two-dimensional extended likelihood analysis, including the dependence of the end-point population on the tau neutrino mass, and allows for the first time an explicit background contribution. We use the decays of the tau to five charged pions and a neutrino and to 3 charged pions, 2 neutral pions and a neutrino to obtain an upper limit of 30 MeV, as well as a preliminary limit of 31 MeV from the decay of a tau to 3 charged hadrons, a neutral pi and a neutrino.