Measurement of tau polarization in e+ e- annihilation at sqrt{s}=58 GeV

TL;DR

This paper reports the measurement of tau lepton polarization and its asymmetry in electron-positron collisions at 58 GeV, providing insights into tau properties and electroweak interactions.

Contribution

First measurement of tau polarization and forward-backward asymmetry at 58 GeV using kinematic distributions of tau decay products.

Findings

Tau polarization measured as 0.012 ± 0.058

Forward-backward asymmetry measured as 0.029 ± 0.057

Results consistent with Standard Model predictions

Abstract

The polarization of tau leptons in the reaction e+ e- --> tau+ tau- has been measured using a e+e- collider, TRISTAN, at the center-of-mass energy of 58 GeV. From the kinematical distributions of daughter particles in tau --> e nu nu-bar, mu nu nu-bar, rho nu or pi(K) nu decays, the average polarization of tau- and its forward-backward asymmetry have been evaluated to be 0.012 +- 0.058 and 0.029 +- 0.057, respectively.