Measurement of direct photon emission in $K^+ \to \pi^+ \pi^0 \gamma$ decay using stopped positive kaons

TL;DR

This paper reports the measurement of the direct photon emission in the decay of stopped positive kaons, providing a branching ratio and observing no interference with internal bremsstrahlung.

Contribution

First measurement of the direct photon emission process in $K^+ o \pi^+ \\pi^0 \\gamma$ decay using stopped kaons, with a quantified branching ratio.

Findings

Branching ratio of direct photon emission: (6.1 ± 2.5 (stat) ± 1.9 (syst)) x 10^{-6}

No interference pattern with internal bremsstrahlung observed

Sample of 4000 events analyzed

Abstract

The radiative decay $K^+ \to \pi^+ \pi^0 \gamma$ ($K_{\pi 2 \gamma}$) has been measured with stopped positive kaons. A $K_{\pi 2 \gamma}$ sample containing 4k events was analyzed, and the $K_{\pi 2 \gamma}$ branching ratio of the direct photon emission process was determined to be $[6.1\pm2.5({\rm stat})\pm1.9({\rm syst})]\times 10^{-6}$. No interference pattern with internal bremsstrahlung was observed.