Search for the lepton number violating process $J/\psi \to K^+K^+e^-e^- +c.c.$

TL;DR

This study searches for a rare lepton number violating decay of the $J/\psi$ particle into two kaons and two electrons, setting a new upper limit on its branching fraction, which provides insights into physics beyond the Standard Model.

Contribution

First experimental search for the lepton number violating decay $J/\psi \to K^+K^+e^-e^-$, establishing the first upper limit on its branching fraction.

Findings

No signal observed, upper limit set at $2.1 \times 10^{-9}$

Provides the first constraint on this lepton number violating process

Enhances understanding of lepton number violation in heavy quarkonium decays

Abstract

Based on $(10087\pm 44)\times10^{6}$ $J/\psi$ events collected with the BESIII detector, we search for the lepton number violating decay $J/\psi \to K^+K^+e^-e^- + c.c.$ for the first time. The upper limit on the branching fraction of this decay is set to be $2.1 \times 10^{-9}$ at the 90$\%$ confidence level with a frequentist method. This is the first search for $J/\psi$ decays with the lepton number change by two, offering valuable insights into the underlying physical processes.