Complete analysis of all $B\to πK$ decays

Abstract

The Standard Model (SM) predicts that ∆A CP , the difference between the direct CP asymmetries for the modes B + → π 0 K + and B 0 → π − K + that are related by weak isospin, should be close to zero. There has been a recent claim by the LHCb Collaboration that the measured value of ∆A CP shows an uncomfortable tension with the SM prediction, almost at the 8σ level. Motivated by this claim, we critically re-examine the data on all the B → πK modes, including the CP asymmetries and CP-averaged branching fractions. From a combined Bayesian analysis with the topological amplitudes and their phases as the free parameters, we find that the best-fit region has a large overlap with the parameter space favoured in the SM, albeit with some enhancement for the electroweak penguin and the coloursuppressed tree amplitudes, consistent with the findings of earlier studies. This 'SM-like' region perfectly explains ∆A CP and hence we conclude that there is not yet enough motivation to go beyond the SM.