Observation of the phi to eta' gamma decay with four charged particles and photons in the final state

TL;DR

This paper reports the first observation of the rare decay phi to eta' gamma, measuring its branching ratio using data from the CMD-2 detector at VEPP-2M.

Contribution

The study provides the first measurement of the branching ratio for phi to eta' gamma decay, utilizing specific decay channels and data collected at low energies.

Findings

First observation of phi to eta' gamma decay

Measured branching ratio: (4.9^{+2.2}_{-1.8} +- 0.6) x 10^{-5}

Data collected at 0.864-1.06 GeV with CMD-2

Abstract

Using 11.6 1/pb of data collected in the energy range 0.864-1.06 GeV by CMD-2 at VEPP-2M, the rare decay mode phi to eta' gamma was observed via the decay chain eta' to pi+pi- eta, eta to pi+pi-pi0 or eta to pi+pi- gamma. The following branching ratio was obtained: Br(phi to eta' gamma) = (4.9^{+2.2}_{-1.8} +- 0.6) \cdot 10^{-5}.