Search for rare Phi decays in pi+ pi_ gamma final state

TL;DR

This paper reports on a search for rare phi meson decays into specific final states, setting upper limits on their branching ratios and exploring potential CP violation effects in eta decays, based on data from the CMD-2 detector.

Contribution

The study provides new upper limits on rare phi decay modes and the eta to pi+ pi- decay, improving constraints on these processes using collider data.

Findings

Upper limit B(phi -> f0(980) gamma) < 1x10^-4 for destructive interference

Upper limit B(phi -> gamma -> pi+ pi- gamma) < 3x10^-5 for gamma > 20 MeV

Measured B(phi -> mu+ mu- gamma) = (2.3+-1.0)x10^-5 for gamma > 20 MeV

Abstract

A search for phi radiative decays has been performed using a data sample of about 2.0 million phi decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From the selected e+ e- -> pi+ pi- gamma events the following results were obtained: B(phi -> f0(980) gamma) < 1x10-4 for destructive and B(phi -> f0(980) gamma) < 7x10-4 for constructive interference with the Bremsstrahlung process respectively, B(phi -> gamma -> pi+ pi- gamma) < 3x10-5 for E of gamma > 20 MeV, B(phi -> rho gamma) < 7x10-4. From the selected e+ e- -> mu+ mu- gamma events B(phi -> mu+ mu- gamma) = (2.3+-1.0)x10-5 has been obtained for E of gamma> 20 MeV. The upper limit on the P,CP-violating decay eta -> pi+ pi- has also been placed: B(eta -> pi+ pi-) < 9x10-4 . All upper limits are at 90 % C.L.