The B→πKB→πK puzzle: 2009 update

The measurements of B→πKB→πK decays have been in disagreement with the predictions of the Standard Model (SM) for some time. In this Letter, we perform an update of this puzzle using the latest (2008) data. We find that the situation has become far less clear. A fit to the B→πKB→πK data alone suggests the presence of new physics (NP). Indeed, if one adds a constraint on the weak phase γ   coming from independent measurements – the SM fit – one finds that the fit is poor. On the other hand, it is not terrible. If one is willing to accept some deficiencies in the fit, it can be argued that the SM can explain the B→πKB→πK data. If one assumes NP, it is found to be present only in the electroweak penguin amplitude, as before. However, the fit is fair at best, and the improvement over the SM is not particularly strong. All and all, while the B→πKB→πK puzzle has not disappeared, it has become weaker.