Measurement of T-odd asymmetry in radiative K+ -> pi0 e+ nu gamma decay using OKA detector

TL;DR

This paper reports a measurement of T-odd asymmetry in the radiative decay of charged kaons, using the OKA detector, to search for CP violation effects with high statistical precision.

Contribution

It provides the first precise measurement of the T-odd correlation in $K^+ ightarrow \pi^{0} e^{+} u_{e} \gamma$ decay, setting limits on asymmetry and CP violation.

Findings

Measured asymmetry $A_{\xi}$ consistent with zero within uncertainties.

Set an upper limit on $|A_{\xi}|$ at 90% confidence level.

Collected over 101,200 candidate decay events.

Abstract

The paper presents a measurement of the T-odd correlation in radiation decay \boldmath $K^+ \rightarrow \pi^{0} e^{+} \nu_{e} \gamma $ performed on the installation of the 101200 candidate events of the investigated decay were identified. Measured correlation $\xi_{\pi e \gamma}$ -is a mixed product of moments $e^{+}$, $\pi^{0}$, $\gamma$ in the kaon rest system, normalized by $M^{3}_{K}$. To assess the asymmetry of the distribution by $\xi_{\pi e \gamma}$ the value used is $A_{\xi}= \frac {N_{+}-N_{-}} {N_{+}+N_{-}}$, where $N_{+(-)}$ is the number of events with $\xi$ greater than (less than) zero. For the $A_{\xi}$ asymmetry, the value is obtained $A_{\xi} = (+0.1 \pm 3.9($stat.$) \pm1.7($syst.$))\times10^{-3}$ or $|A_{\xi}| < 5.4\times10^{-3} (90\%~ CL)$