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First evidence for the decay Bºs → μ+μ-
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LHCb Collaboration (Including: Back, J. J., Craik, Daniel, Dossett, D., Gershon, T. J., Harrison, P. F., Kreps, Michal, Latham, Thomas, Pilar, T., Poluektov, Anton, Reid, Matthew M., Silva Coutinho, R., Whitehead, M. (Mark) and Williams, M. P.). (2013) First evidence for the decay Bºs → μ+μ-. Physical Review Letters, Volume 110 (Number 2). Article number 021801 . doi:10.1103/PhysRevLett.110.021801 ISSN 0031-9007.
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WRAP_LHCb_PhysRevLett.110.021801.pdf - Published Version Available under License Creative Commons Attribution. Download (372Kb) | Preview |
Official URL: http://dx.doi.org/10.1103/PhysRevLett.110.021801
Abstract
A search for the rare decays Bºs → μ+μ- and Bº→μ+μ- is performed with data collected in 2011 and 2012 with the LHCb experiment at the Large Hadron Collider. The data samples comprise 1.1 fb-1 of proton-proton collisions at √s=8 TeV and 1.0 fb-1 at √s=7 TeV. We observe an excess of Bºs → μ+μ- candidates with respect to the background expectation. The probability that the background could produce such an excess or larger is 5.3×10-4 corresponding to a signal significance of 3.5 standard deviations. A maximum-likelihood fit gives a branching fraction of B(Bºs → μ+μ-)=(3.2-1.2+1.5)×10-9, where the statistical uncertainty is 95% of the total uncertainty. This result is in agreement with the standard model expectation. The observed number of Bº→μ+μ- candidates is consistent with the background expectation, giving an upper limit of B(Bº→μ+μ-)<9.4×10-10 at 95% confidence level.
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