Search for the rare decay \( K_{\mathrm{S}}^0\to {\mu^{+}}{\mu^{-}} \)

Abstract

A search for the decay \( K_{\mathrm{S}}^0\to {\mu^{+}}{\mu^{-}} \) is performed, based on a data sample of 1.0 fb−1 of pp collisions at \( \sqrt{s}=7\;\mathrm{TeV} \) collected by the LHCb experiment at the Large Hadron Collider. The observed number of candidates is consistent with the background-only hypothesis, yielding an upper limit of \( \mathcal{B}\left( {K_{\mathrm{S}}^0\to {\mu^{+}}{\mu^{-}}} \right) \) < 11(9) × 10−9 at 95 (90)% confidence level. This limit is a factor of thirty below the previous measurement.

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