Measurement of Direct Photon Emission in K^+ -> pi^+ pi^0 gamma Decay

TL;DR

This paper reports a precise measurement of the direct photon emission in K^+ -> pi^+ pi^0 gamma decay, providing a branching ratio and analyzing the decay spectrum to understand the underlying processes.

Contribution

The study presents the first detailed measurement of the direct photon emission component in this decay mode with a large event sample and no interference effects observed.

Findings

Branching ratio for direct photon emission: (4.7±0.8±0.3) x 10^{-6}

No interference component detected in the decay spectrum

Approximately 20,000 decay events observed

Abstract

We have performed a measurement of the K^+ -> pi^+ pi^0 gamma decay and have observed 2 X 10^4 events. The best fit to the decay spectrum gives a branching ratio for direct photon emission of (4.7\pm0.8\pm0.3) X 10^{-6} in the pi^+ kinetic energy region of 55 to 90 MeV and requires no component due to interference with inner bremsstrahlung.