Search for C-parity violation in $J/ \psi \to \gamma\gamma$ and $ \gamma \phi$

TL;DR

This study searches for C-parity violation in specific J/psi decays using a large dataset, finding no signals but setting the most stringent upper limits to date, including the first limit on one decay mode.

Contribution

First search for C-parity violation in J/psi decays to gamma gamma and gamma phi, establishing new upper limits with improved sensitivity.

Findings

No significant signals observed in either decay channel.

Upper limits on branching fractions are set at 2.7×10^{-7} and 1.4×10^{-6}.

First limit established for J/psi to gamma phi decay.

Abstract

Using $1.06\times10^8$ $\psi(3686)$ events recorded in $e^{+}e^{-}$ collisions at $\sqrt{s}=$ 3.686 GeV with the BESIII at the BEPCII collider, we present searches for C-parity violation in $J/\psi \to \gamma\gamma$ and $ \gamma \phi$ decays via $\psi(3686) \to J/\psi \pi^+\pi^-$. No significant signals are observed in either channel. Upper limits on the branching fractions are set to be $\mathcal{B}(J/\psi \to \gamma\gamma) < 2.7 \times 10^{-7}$ and $\mathcal{B}(J/\psi \to \gamma\phi) < 1.4 \times 10^{-6}$ at the 90\% confidence level. The former is one order of magnitude more stringent than the previous upper limit, and the latter represents the first limit on this decay channel.