Analysis of $J/\psi(\eta_c)\to \gamma ~+$ invisible decays in the standard model

TL;DR

This paper calculates the standard model background for the invisible decay of $J/$ and $_c$ into a photon and neutrinos, showing it is much lower than current experimental limits, leaving room for new physics.

Contribution

It provides the first lowest-order standard model calculation of $J/\psi$ and $\eta_c$ decays into a photon and neutrinos, clarifying the background for experimental searches.

Findings

Branching ratio for $J/\psi\to \gamma \nu\bar{\nu}$ is far below experimental limits.

Standard model background is negligible, suggesting potential for new physics detection.

Analysis of $\eta_c\to \gamma \nu\bar{\nu}$ complements the $J/\psi$ study.

Abstract

Motivated by the experimental study of $J/\psi\to\gamma ~+$ invisible decay by the CLEO Collaboration, we analyze the process $J/\psi\to \gamma \nu\bar{\nu}$, as the standard model background for this invisible decay, at the lowest order. Our investigation shows that Br($J/\psi\to \gamma \nu\bar{\nu}$) is far below the present experimental upper limit on the branching ratio of $J/\psi\to\gamma ~+$ invisible, which indicates that some interesting room for new physics in this channel might be expected. We also present a similar analysis of the $\eta_c\to \gamma \nu\bar{\nu}$ decay.