Hint of lepton flavour non-universality in B meson decays

A bstract The LHCb collaboration has recently presented their result on R K = ℬ( B + → K + μ + μ − ) / ℬ( B + → K + e + e − ) for the dilepton invariant mass bin m ℓℓ 2 = 1 − 6 GeV 2 ( ℓ = μ, e ). The measurement shows an intriguing 2 . 6 σ deviation from the Standard Model (SM) prediction. In view of this, we study model independent New Physics (NP) explanations of R K 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.