Large electroweak penguins in B --> pi pi and B --> pi K : implication for new physics

Abstract

We show that the anomalies in the $B\to\pi\pi$ decay channels, {\em viz.}, the large branching ratio of $B\to\pi^0\pi^0$ and large direct CP asymmetry of $B\to\pi^+\pi^-$, can both be explained, even in the framework of existing theoretical models which predict the relative strengths of the tree and the strong penguin amplitudes, if there is an abnormally large electroweak penguin contribution. We also critically examine the expectation of a similarly large electroweak penguin in the $B\to\pi K$ sector, and show that it can be accomodated, and may even be motivated from an SU(3) flavor symmetry between the $B\to\pi\pi$ and the $B\to\pi K$ amplitudes, but is not necessary to explain the data. We emphasize that if the experimental numbers on these charmless nonleptonic channels survive, they may turn out to be an indirect signal of new physics. Current data is insufficient to discriminate betwen flavor-specific and flavor-blind new physics scenarios.