Measurement of the B0 s → μ + μ − Branching Fraction and Effective Lifetime and Search for B0 → μ + μ − Decays

LHCb Collaboration, R Aaij, Marco Adinolfi, Emma Buchanan, Andrew Cook, Jeremy Dalseno, Sam Harnew, James Kariuki, Paras Naik, Konstantinos Petridis, Gabriela Pomery, Eugenia Price, Claire Prouve, Renato Quagliani, Jonas Rademacker, Daniel Saunders, Nicola Skidmore, Jaap Velthuis

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A search for the rare decays B0 s → μþμ− and B0 → μþμ− is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb−1. An excess of B0 s → μþμ− decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be BðB0 s → μþμ−Þ¼ð3.0 0.6þ0.3 −0.2 Þ × 10−9, where the first uncertainty is statistical and the second systematic. The first measurement of the B0 s → μþμ− effective lifetime, τðB0 s → μþμ−Þ ¼ 2.04 0.44 0.05 ps, is reported. No significant excess of B0 → μþμ− decays is found, and a 95% confidence level upper limit, BðB0→ μþμ−Þ < 3.4 × 10−10, is determined. All results are in agreement with the standard model expectations. D
Original languageEnglish
JournalPhysical Review Letters
Publication statusPublished - 11 May 2017


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