Hint of lepton flavour non-universality in B meson decays

Abstract

Abstract: The LHCb collaboration has recently presented their result on RK = ℬ(B+ → K+μ+μ−)/ ℬ(B+ → K+e+e−) for the dilepton invariant mass bin mℓℓ2 = 1 − 6 GeV2 (ℓ = μ, e). The measurement shows an intriguing 2.6σ deviation from the Standard Model (SM) prediction. In view of this, we study model independent New Physics (NP) explanations of RK consistent with other measurements involving b → sℓ+ℓ− transition, relaxing the assumption of lepton universality. We perform a Bayesian statistical fit to the NP Wilson Coefficients and compare the Bayes Factors of the different hypotheses in order to quantify their goodness-of-fit. We show that the data slightly favours NP in the muon sector over NP in the electron sector.