Search for the rare decay $\Lambda_{c}^{+} \to p\mu^+\mu^-$.

A search for the flavor-changing neutral-current decay $\Lambda_{c}^{+} \to p\mu^+\mu^-$ is reported using a data set corresponding to an integrated luminosity of $3.0\rm fb^{-1}$ collected by the LHCb collaboration. No significant signal is observed outside of the dimuon mass regions around the $\phi$ and $\omega$ resonances and an upper limit is placed on the branching fraction of $\mathcal{B} (\Lambda_{c}^{+} \to p\mu^+\mu^-) < 7.7~(9.6)\times 10^{-8}~{\rm at}~90\%~(95\%)$ confidence level. A significant signal is observed in the $\omega$ dimuon mass region for the first time.