B → Kπ decays and the weak phase angle γ

The large branching ratios for B --> K pi decays as observed by the CLEO Collaboration indicate that penguin interactions contribute a major part to the decay rates and provide an interference between the Cabibbo-suppressed tree and penguin contributions resulting in a CP-asymmetry between the B --> K pi and its charge conjugate mode. The CP-averaged decay rates depend also on the weak phase gamma and give us a determination of this phase. In this talk, I would like to report on a recent analysis of B --> K pi decays using factorisation model with final state interaction phase shift included. We find that factorisation seems to describe qualitatively the latest CLEO data. We also obtain a relation for the branching ratios independent of the strength of the strong penguin interactions. This relation gives a central value of 0.60 x 10(-5) for beta((B) over bar (0) --> ($) over bar (0) pi (0)), somewhat smaller than the latest CLEO measurement. We also find that a ratio obtained from the CP-averaged B --> K pi decay rates could be used to test the factorisation model and to determine the weak angle gamma with more precise data, though the latest CLEO data seem to favor gamma in the range 90 degrees - 120 degrees.