A search for $B_s^0\to {\mu }^{+}{\mu }^{-}$ and $B^0\to {\mu }^{+}{\mu }^{-}$ decays is performed using $1.0{\mathrm{fb}}^{-1}$ of $pp$ collision data collected at $\sqrt{s}=7\mathrm{TeV}$ with the LHCb experiment at the Large Hadron Collider. For both decays, the number of observed events is consistent with expectation from background and standard model signal predictions. Upper limits on the branching fractions are determined to be $\mathcal{B}(B_s^0\to {\mu }^{+}{\mu }^{-})<4.5(3.8)\times {10}^{-9}$ and $\mathcal{B}(B^0\to {\mu }^{+}{\mu }^{-})<1.0(0.81)\times {10}^{-9}$ at 95% (90%) confidence level.

• Received 20 March 2012

DOI:https://doi.org/10.1103/PhysRevLett.108.231801

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© 2012 CERN, for the LHCb Collaboration