Search for the lepton number violating process $J/\ddot{I}ˆ\to K^{+}{K}^{+}{e}^{-}{e}^{-}+c.c.$

Abstract

Based on $(10087\pm 44)\times 10^6$ $J/\ddot{I}ˆ$ events collected with the BESIII detector, we search for the lepton number violating decay $J/\ddot{I}ˆ\to K^{+}{K}^{+}{e}^{-}{e}^{-}+c.c.$ 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 $J/\ddot{I}ˆ$ decays with the lepton number change by two, offering valuable insights into the underlying physical processes.

9 pages, 3 figures