2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47518We present new constraints on the mass $m_{ν_τ}$ of the tau neutrino and its mixing with a fourth generation neutrino. From an analysis of the partial widths of tau lepton decays we obtain the following bounds at the 90% confidence level: $m_{ν_τ} < 32$ MeV and $\sin^2θ< 0.007$, where $θ$ describes the Cabibbo-like mixing of the third and fourth generation neutrinos.2 pages, no figures. Submitted to Phys. Rev. DHigh Energy Physics - Phenomenologytext