DOIAbstract
International audienceIn this report, measurements of the ratios of branching fractions RK=B(B+→K+μ+μ−)/B(B+→K+e+e−) and R(D⁎)=B(B‾0→D⁎+τ−ν‾τ)/B(B‾0→D⁎+μ−ν‾μ) , as well as preliminary upper limits on the B(s)0→τ+τ− branching fractions are presented, using proton–proton collision data corresponding to an integrated luminosity of 3.0 fb −1 recorded by the LHCb experiment during 2011 and 2012. The value of RK is measured to be 0.745−0.074+0.090 (stat) ± 0.036 (syst), R(D⁎) equals 0.336 ± 0.027 (stat) ± 0.030 (syst), and at 95% confidence level B(Bs0→τ+τ−)<3.0×10−3 and B(B0→τ+τ−)<1.3×10−3 . The results for RK and R(D⁎) are respectively −2.6 and +2.1 standard deviations away from the values expected from lepton universality of the Standard Model
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