Constraining Penguin Contributions and the CKM Angle γ through B d → π + π −

The decays Bd → ππ and Bs → KK provide an interesting strategy to extract the CKM angle γ at “second-generation” B-physics experiments of the LHC era. A variant for “first-generation” experiments can be obtained, if Bs → KK is replaced by Bd → πK. We show that the most recent experimental results for the CP-averaged Bd → ππ and Bd → πK branching ratios imply a rather restricted range for the corresponding penguin parameters, and upper bounds on the direct CP asymmetries Adir CP(Bd → ππ) and Adir CP(Bd → πK). Moreover, we point out that interesting constraints on γ can be obtained from the CP-averaged Bd → ππ and Bd → πK branching ratios, if in addition mixinginduced CP violation in the former decay is measured, and the B d–B 0 d mixing phase is fixed through Bd → J/ψKS. An extraction of γ becomes possible, if furthermore direct CP violation in Bd → ππ or Bd → πK is observed. ∗ E-mail: [email protected]