Hint of lepton flavour non-universality in B meson decays

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

Composite leptoquarks and anomalies in B -meson decays

We attempt to explain recent anomalies in semileptonic B decays at LHCb via a composite Higgs model, in which both the Higgs and an SU(2) L -triplet leptoquark arise as pseudo-Goldstone bosons of the strong dynamics. Fermion masses are assumed to be generated via the mechanism of partial compositeness, which largely determines the leptoquark couplings and implies non-universal lepton interactions. The latter are needed to accommodate tensions in the b → sμμ dataset and to be consistent with a discrepancy measured at LHCb in the ratio of B + → K + μ + μ − to B + → K + e + e − branching ratios. The data imply that the leptoquark should have a mass of around a TeV. We find that the model is not in conflict with current flavour or direct production bounds, but we identify a few observables for which the new physics contributions are close to current limits and where the leptoquark is likely to show up in future measurements. The leptoquark will be pair-produced at the LHC and decay predominantly to third-generation quarks and leptons, and LHC13 searches will provide further strong bounds