A Study of the Radiative Ke3 Decay and Search for Direct Photon Emission with the KLOE Detector

TL;DR

This paper reports a precise measurement of the ratio of radiative to non-radiative KL decays and the first assessment of direct photon emission in semileptonic decays using the KLOE detector at DAFNE.

Contribution

It provides the first measurement of direct emission contribution in KL semileptonic decays and refines the ratio of radiative to non-radiative decay widths.

Findings

Measured R = (924 ± 23(stat) ± 16(syst)) x 10^{-5}

Determined direct emission parameter X = -2.3 ± 1.3(stat) ± 1.4(syst)

Analyzed about 3.5 million Ke3(g) events

Abstract

We present a measurement of the ratio R = \Gamma(\keg;\Estar>30\mev,\qstar>20^\circ)$/$\Gamma(\kegf)$ and a first measurement of the direct emission contribution in KL semileptonic decays. The measurement is done at the DAFNE phi-factory selecting phi->KL KS decays with the KLOE detector. We use 328 pb^{-1}$ of data corresponding to about 3.5 million Ke3(g) events and about 9000 radiative events. Our result is R=(924 +/- 23(stat) +/-16(syst)10^{-5} for the branching ratio and X=-2.3 +/- 1.3(stat) +/- 1.4(syst) for the parameter describing direct emission.