Measurement of K^+ \to \pi^0 \mu^+ \nu \gamma decay using stopped kaons

TL;DR

This paper reports the measurement of the rare decay K^+ to pi^0 mu^+ nu gamma using stopped kaons, providing experimental data that aligns well with theoretical models.

Contribution

First measurement of the K^+ o \pi^0 \mu^+ u \gamma decay with stopped kaons, offering new experimental data for this rare process.

Findings

Observed 125 decay events.

Measured partial branching ratio of (2.4 ± 0.5(stat) ± 0.6(syst))×10^{-5}.

Results agree with theoretical predictions.

Abstract

The K^+ \to \pi^0 \mu^+ \nu \gamma ($K_{\mu 3 \gamma}$) decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A $K_{\mu 3 \gamma}$ sample containing 125 events was obtained. The partial branching ratio $Br(K_{\mu 3 \gamma}, E_{\gamma}>30 {\rm MeV}, \theta_{\mu^+ \gamma}>20^{\circ})$ was found to be $[2.4 \pm 0.5(stat) \pm 0.6(syst)]\times 10^{-5}$, which is in good agreement with theoretical predictions.