Testing the HyperCP anomaly at LHCb: evidence for the $Sigma^+ to p mu^+ mu^-$ decay

A search for $Sigma^+ to p mu^+ mu^-$ decays with LHCb Run 1 data is presented, yielding an evidence for this decay and a measurement of a branching fraction compatible with the Standard Model. The HyperCP anomaly in the dimuon invariant mass distribution is not confirmed, and its branching fraction central value is excluded at 95% CL. Prospects for the future of this measurement in LHCb are also presented.