A search for the rare decays Bs0→μ+μ- and B0→μ+μ- is performed at the LHCb experiment. The data analyzed correspond to an integrated luminosity of 1 fb-1 of pp collisions at a center-of-mass energy of 7 TeV and 2 fb-1 at 8 TeV. An excess of Bs0→μ+μ- signal candidates with respect to the background expectation is seen with a significance of 4.0 standard deviations. A time-integrated branching fraction of B(Bs0→μ+μ-)=(2.9-1.0+1.1)×10 -9 is obtained and an upper limit of B(B0→μ+μ -)<7.4×10-10 at 95% confidence level is set. These results are consistent with the standard model expectations. © 2013 CERN, for the LHCb Collaboration Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
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