New constraints on the tau neutrino mass and fourth generation mixing

TL;DR

This paper establishes new experimental limits on the tau neutrino mass and its mixing with a hypothetical fourth-generation neutrino, refining our understanding of neutrino properties.

Contribution

It provides the first constraints on tau neutrino mass and mixing with a fourth generation based on tau decay data.

Findings

Tau neutrino mass less than 32 MeV at 90% confidence

Mixing angle squared less than 0.007 at 90% confidence

Improved bounds compared to previous measurements

Abstract

We present new constraints on the mass $m_{\nu_\tau}$ 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: $m_{\nu_\tau} < 32$ MeV and $\sin^2\theta < 0.007$, where $\theta$ describes the Cabibbo-like mixing of the third and fourth generation neutrinos.