Experimental study of direct photon emission in K- --> pi- pi0 gamma decay using ISTRA+ detector

TL;DR

This study measures the branching ratio of direct photon emission in K- decay using the ISTRA+ detector, providing experimental data that compares with previous experiments and theoretical models.

Contribution

First measurement of the branching ratio for direct photon emission in K- decay using in-flight decays with the ISTRA+ detector.

Findings

Measured Br(DE) = (0.37 ± 0.39(stat) ± 0.10(syst)) × 10^(-5)

Result consistent with stopped-kaon experiments, but differs from other in-flight experiments

Data compared with recent theoretical predictions

Abstract

The branching ratio in the charged-pion kinetic energy region of 55 to 90 MeV for the direct photon emission in the K- --> pi- pi0 gamma decay has been measured using in-flight decays detected with the ISTRA+ setup operating in the 25 GeV/c negative secondary beam of the U-70 PS. The value Br(DE)=[0.37+-0.39(stat)+-0.10(syst)]*10^(-5) obtained from the analysis of 930 completely reconstructed events is consistent with the average value of two stopped-kaon experiments, but it differs by 2.5 standard deviations from the average value of three in-flight-kaon experiments. The result is also compared with recent theoretical predictions.