Recent results from CLEO on $B\to K\pi$ indicate that the phase $\gamma$ may be substantially different from that obtained from other fit to the KM matrix elements in the standard model. We show that $\gamma$ extracted using $B\to K\pi ,\pi \pi$ is sensitive to new physics occurring at loop level. It provides a powerful method to probe new physics in electroweak penguin interactions. Using effects due to anomalous gauge couplings as an example, we show that within the allowed ranges for these couplings information about $\gamma$ obtained from $B\to K\pi ,\pi \pi$ can be very different from the standard model prediction.

• Received 11 May 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.18