Upper Limit on theντMass

Abstract

We have set an upper limit on the ${\nu }_{\tau }$ mass from a study of the four-pion invariant-mass distribution in the decay $\tau \to 3{\pi }^{\pm }{\pi }^0{\nu }_{\tau }$. We obtain the limit ${m_{\nu }}_{\tau }<164\mathrm{}$ MeV/${\mathit{c}}^2$ at 95% confidence level.