Search for the lepton number violation decay $\phi \to \pi^+ \pi^+ e^- e^-$ via $J/\psi\to \phi\eta$

TL;DR

This study searches for a rare lepton number violating decay of the phi meson using a large dataset of J/psi events, setting a new upper limit on its branching fraction.

Contribution

First search for the lepton number violating decay $ ext{phi} o ext{pi}^+ ext{pi}^+ e^- e^-$ via $J/\psi$ decays, establishing an upper limit on its branching fraction.

Findings

No signal observed for the decay.

Upper limit on branching fraction set at $9.7 imes 10^{-6}$.

Data sample of over 10 billion $J/\psi$ events used.

Abstract

Using $(1.0087\pm0.0044)\times10^{10}$ $J/\psi$ events collected by the BESIII detector at the BEPCII collider, we search for the lepton number violation decay $\phi \to \pi^+ \pi^+ e^- e^-$ via $J/\psi\to \phi\eta$. No signal is found and the upper limit on the branching fraction of $\phi \to \pi^+ \pi^+ e^- e^-$ is set to be $9.7\times10^{-6}$ at the 90\% confidence level.