Utilising $B \to \pi K$ Decays at the High-Precision Frontier

Abstract

B → πK decays have received a lot of attention over the last two decades, with puzzling patterns in the previous data. They form a particularly interesting set of decays as they are dominated by QCD penguin topologies. Electroweak penguin amplitudes also play a significant role, giving a contribution at the level of the tree topologies. We find a discrepancy in the correlation between the CP asymmetries of B 0 d → π 0 K S . A modified electroweak penguin sector offers an attractive avenue for new particles to enter. We provide a new method to determine the electroweak penguin parameters, and apply it to current data for charged B → πK decays. It uses an isospin relation and requires only SU(3) input to fix a normalization. A central role is played by the mixing-induced CP asymmetry of B 0 d → π 0 K S . The implementation of our strategy in the high-precision era of B-physics has the exciting potential to establish New Physics in the electroweak penguin sector.