Measurement of the Lifetime of the Tau Lepton

TL;DR

This paper reports a precise measurement of the tau lepton's lifetime using LEP data, supporting lepton universality and deriving the strong coupling constant alpha_s from tau decay data.

Contribution

The study provides a new, precise measurement of the tau lepton lifetime and confirms lepton universality at a high level of accuracy, also estimating alpha_s from tau decay.

Findings

Tau lifetime measured as 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs.

Supports lepton universality at six per mille level.

Determines alpha_s(m_tau^2) = 0.319 +/- 0.015 (exp.) +/- 0.014 (theory).

Abstract

The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in tau_tau = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this result with the muon lifetime supports lepton universality of the weak charged current at the level of six per mille. Assuming lepton universality, the value of the strong coupling constant, alpha_s is found to be alpha_s(m_tau^2) = 0.319 +/- 0.015(exp.) +/- 0.014 (theory).