\psi(2S) Decays into $\J$ plus Two Photons

TL;DR

This paper measures branching fractions of various decay modes of the \\psi(2S) particle into J/psi with two photons, using data from BESII, providing precise experimental results for these rare decays.

Contribution

The study provides the first precise measurements of branching fractions for \\psi(2S) decays into J/psi with two photons, enhancing understanding of charmonium decay processes.

Findings

Branching fraction for \\psi(2S) \\to \\pi^0 J/\\psi: (1.43 \\pm 0.14 \\pm 0.13) x 10^{-3}

Branching fraction for \\psi(2S) \\to \\eta J/\\psi: (2.98 \\pm 0.09 \\pm 0.23)%

Branching fractions for \\psi(2S) \\to \\gamma \\chi_{c1,2} \\to \\gamma \\gamma J/\\psi: (2.81 \\pm 0.05 \\pm 0.23)% and (1.62 \\pm 0.04 \\pm 0.12)% respectively

Abstract

Using $\gamma \gamma J/\psi, J/\psi \ra e^+ e^-$ and $\mu^+ \mu^-$ events from a sample of $14.0\times 10^6$ $\psip$ decays collected with the BESII detector, the branching fractions for $\psip\ra \pi^0\J$, $\eta\J$, and $\psi(2S)\ar\gamma\chi_{c1},\gamma\chi_{c2}\ar\gamma\gamma\jpsi$ are measured to be $B(\psip\ra \pi^0\J) = (1.43\pm0.14\pm0.13)\times 10^{-3}$, $B(\psip\ra \eta\J) = (2.98\pm0.09\pm0.23)%$, $B(\psi(2S)\ar\gamma\chi_{c1}\ar\gamma\gamma\jpsi) = (2.81\pm0.05\pm 0.23)%$, and $B(\psi(2S)\ar\gamma\chi_{c2}\ar\gamma\gamma\jpsi) = (1.62\pm0.04\pm 0.12)%$.