Improved limit on the branching fraction of the rare decay K⁰_s→μ⁺μ^-

A search for the decay KS0→μ+μ- is performed, based on a data sample of proton-proton collisions corresponding to an integrated luminosity of 3fb-1, collected by the LHCb experiment at centre-of-mass energies of 7 and 8TeV. The observed yield is consistent with the background-only hypothesis, yielding a limit on the branching fraction of B(KS0→μ+μ-)<0.8(1.0)×10-9 at 90%(95%) confidence level. This result improves the previous upper limit on the branching fraction by an order of magnitude.