The B -> pi K Puzzle: 2009 Update

TL;DR

This paper updates the status of the B -> pi K decay puzzle with 2008 data, finding the discrepancy with the Standard Model less clear and suggesting possible new physics mainly in electroweak penguin amplitudes.

Contribution

It provides an updated analysis of B -> pi K decays, assessing the potential need for new physics and the fit quality with recent data.

Findings

Discrepancy with SM has lessened with new data

Possible new physics in electroweak penguin amplitudes

Fit quality is fair but not conclusive

Abstract

The measurements of B -> pi K decays have been in disagreement with the predictions of the Standard Model (SM) for some time. In this paper, 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 -> pi K data alone suggests the presence of new physics (NP). Indeed, if one adds a constraint on the weak phase gamma 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 -> pi K 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 -> pi K puzzle has not disappeared, it has become weaker.