First measurement of the T-violating muon polarization in the decay K^+ --> mu^+ nu gamma

TL;DR

This paper reports the first measurement of T-violating muon polarization in K^+ decay, providing a new test for CP-violation beyond the Standard Model, with results consistent with no T-violation.

Contribution

It presents the first experimental measurement of muon polarization in K^+ decay, probing new sources of CP-violation in the Higgs sector.

Findings

Measured P_T = (-0.64 +- 1.85(stat) +- 0.10(syst)) x 10^{-2}

Results are consistent with no T-violation

Provides constraints on new CP-violation sources in Higgs sector

Abstract

We present the result of the first measurement of the T-violating muon polarization P_T in the decay K^+ --> mu^+ nu gamma. This polarization is sensitive to new sources of CP-violation in the Higgs sector. Using data accumulated in the period 1996-98 we have obtained P_T = (-0.64 +- 1.85(stat) +- 0.10(syst))x10^{-2} which is consistent with no T-violation in this decay.