A Precise Measurement of the Tau Lifetime

TL;DR

This paper reports a precise measurement of the tau lepton lifetime using data from the DELPHI detector at LEP, employing multiple decay channels and combining results for an improved accuracy.

Contribution

It provides the most precise measurement of the tau lifetime by combining multiple decay modes and previous results from the DELPHI experiment.

Findings

Tau lifetime measured as 290.9 +/- 1.4 (stat) +/- 1.0 (sys) fs.

Used multiple decay channels for improved accuracy.

Combined new measurements with previous data for a precise result.

Abstract

The tau lepton lifetime has been measured with the e+e- -> tau+tau- events collected by the DELPHI detector at LEP in the years 1991-1995. Three different methods have been exploited, using both one-prong and three-prong tau decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave tau_tau (1 prong) = 291.8 +/- 2.3 (stat) +/- 1.5 (sys) fs. A third measurement using taus which decayed to three charged particles yielded tau_tau (3 prong) = 288.6 +/- 2.4 (stat) +/- 1.3 (sys) fs. These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be tau_tau = 290.9 +/- 1.4 (stat) +/- 1.0 (sys) fs.