Observation of J/psi --> 3 gamma

TL;DR

This paper reports the first observation of the decay J/psi --> 3 gamma with a significant statistical signal, measuring its branching fraction using data from the CLEO-c detector at CESR.

Contribution

It provides the first experimental evidence of the J/psi decay into three photons, expanding understanding of charmonium decay modes.

Findings

First observation of J/psi --> 3 gamma decay

Branching fraction measured as (1.2 +- 0.3 +- 0.2) x 10^-5

Statistical significance of 6 sigma

Abstract

We report the first observation of the decay J/psi --> 3 gamma. The signal has a statistical significance of 6 sigma and corresponds to a branching fraction of B(J/psi --> 3 gamma) = (1.2 +- 0.3 +- 0.2) x 10^-5, in which the errors are statistical and systematic, respectively. The measurement uses psi(2S) --> pi+ pi- J/psi events acquired with the CLEO-c detector operating at the CESR e+e- collider.