Measurement of P_{mu}xi in Polarized Muon Decay

TL;DR

This paper reports a highly precise measurement of the muon decay parameter P_{mu}^{pi}xi, confirming Standard Model predictions and constraining alternative theories like left-right symmetric models.

Contribution

The study provides the most precise measurement of P_{mu}^{pi}xi to date, improving accuracy over previous results and testing fundamental symmetries in particle physics.

Findings

Measurement of P_{mu}^{pi}xi = 1.0003 ± 0.0006 (stat) ± 0.0038 (syst)

Results agree with Standard Model predictions

Constraints placed on left-right symmetric models

Abstract

The quantity P_{mu}^{pi}xi, where xi is one of the muon decay parameters and $P_{\mu}^{\pi}$ is the degree of muon polarization in pion decay, has been measured. The value P_{mu}^{pi}xi = 1.0003 +- 0.0006 stat. +- 0.0038 syst. was obtained. This result agrees with previous measurements but is over a factor of two more precise. It also agrees with the Standard Model prediction for P_{mu}^{pi}xi and thus leads to restrictions on left-right symmetric models.