Abstract
The anomalies in rare B decays endure. We present results of an updated global analysis that takes into account the latest experimental input – in particular the recent results on R_K and BR(B_s rightarrow mu ^+mu ^-) – and that qualitatively improves the treatment of theory uncertainties. Fit results are presented for the Wilson coefficients of four-fermion contact interactions. We find that muon specific Wilson coefficients C_9 simeq -0.73 or C_9 = -C_{10} simeq -0.39 continue to give an excellent description of the data. If only theoretically clean observables are considered, muon specific C_{10} simeq 0.60 or C_9=-C_{10} simeq -0.35 improve over the Standard Model by sqrt{Delta chi ^2} simeq 4.7sigma and sqrt{Delta chi ^2} simeq 4.6sigma , respectively. In various new physics scenarios we provide predictions for lepton flavor universality observables and CP asymmetries that can be tested with more data. We update our previous combination of ATLAS, CMS, and LHCb data on BR(B_s rightarrow mu ^+mu ^-) and BR(B^0rightarrow mu ^+mu ^-) taking into account the full two-dimensional non-Gaussian experimental likelihoods.
Highlights
Since several years there exist persistent discrepancies between the Standard Model (SM) predictions and the experimental results for rare decays of B mesons based on the neutral current b → s transitions
We find that muon specific Wilson coefficients C9 −0.73 or C9 = −C10 −0.39 continue to give an excellent description of the data
The CP averaged angular observables Si, the CP asymmetries Ai, and the lepton flavor universality (LFU) ratios can be written in terms of ratios of second order polynomials, while the Pi observables involve irrational functions. In those cases we obtain an approximation of the covariance matrix for the observables by expanding the functions to second order in the Wilson coefficients and following the same procedure as for the branching ratios. We find that this procedure gives reliable estimates as long as the absolute values of the new physics Wilson coefficients are somewhat smaller than the corresponding relevant SM coefficients
Summary
Since several years there exist persistent discrepancies between the Standard Model (SM) predictions and the experimental results for rare decays of B mesons based on the neutral current b → s transitions. The LHCb collaboration presented updated results for two theoretically clean observables that have previously shown tensions with the SM predictions: the LFU ratio RK and the branching ratio BR(Bs → μ+μ−). In our previous studies [6,22,23,24] we have evaluated theory uncertainties and their correlations for the Wilson coefficients fixed to their SM values This is typically a good approximation as long as the best fit results are in the vicinity of the SM point. 2 we discuss in detail the improved treatment of theory uncertainties and illustrate the size of the effect in the case of LFU observables and CP asymmetries in the presence of new physics. Our combination of the experimental results on the Bs → μ+μ− branching ratio is described in Appendix A
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