The penguin operators in nonresonant $B^- \to M \bar M π^-$ $(M =π^-, K^-, K^0)$ decays

We investigate the contributions coming from the penguin operators in the nonresonant $B^- \to M \bar M π^-$ ($M =π^-, K^-, K^0$) decays. The effective Wilson coefficients of the the strong penguin operators $O_{4,6}$ are found to be relatively larger. We calculate the contributions arising from the $O_4$ and $O_6$ operators in the nonresonant decays $B^- \to M \bar Mπ^-$ ($M = π^-, K^-, \bar K^0$) using a model combining heavy quark symmetry and the chiral symmetry, developed previously. We find that the forbidden nonresonant $B^- \to K^0 \bar K^0 π^-$ decay occurs through the strong penguin operators. These penguin contributions affect the branching ratios for $B^- \to M \bar Mπ^-$ ($M = π^-, K^-$) by only a few percent. The branching ratio for $B^- \to K^0 \bar K^0 π^-$ is estimated to be of the order $ 10^{-6}$.