Search for the decay phi -> K0 K0bar gamma with the KLOE experiment

TL;DR

This paper reports a search for the rare decay phi -> K0 K0bar gamma using the KLOE detector, setting an upper limit on its branching ratio due to the absence of significant signal events.

Contribution

The study provides the first experimental upper limit on the branching ratio of phi -> K0 K0bar gamma decay, constraining theoretical models of this process.

Findings

Observed 5 candidate events against an expected background of 3.2.

Set an upper limit on the branching ratio: < 1.9 x 10^-8 at 90% C.L.

No significant signal detected for the decay process.

Abstract

We have searched for the decay phi -> K0 K0bar gamma, by detecting K_s pairs plus a photon and with the K_s-mesons decaying to pi^+ pi^-, in a sample of about 1.5x 10^9 phi-decays collected by the KLOE experiment at DAFNE. The reaction proceeds through the intermediate states f_0(980) gamma, a_0(980) gamma. We find five events with 3.2 events expected from background processes. We obtain the upper limit: BR (phi -> K0 K0bar gamma) < 1.9x10^-8 at 90% C.L. .