Search for the lepton number violating process $\Xi^- \rightarrow \Sigma^+ e^- e^- +c.c.$

Abstract

We present a search for the lepton number violating decay $\Xi^-\rightarrow\Sigma^+e^-e^- +c.c.$ with $(10087\pm44)\times10^6$ $J/\psi$ events collected by the BESIII detector at the BEPCII collider. Employing a blind analysis strategy, no significant signal is observed above the expected background yield. The upper limit on the branching fraction is determined to be ${\rm Br}(\Xi^-\rightarrow\Sigma^+e^-e^-+c.c.)< 2.0\times10^{-5}$ at the $90\%$ confidence level.