Final State Interactions in Hadronic B Decays

There exist many experimental indications that final-state interactions (FSIs) may play a prominent role not only in charmful B decays but also in charmless B ones. We examine the final-state rescattering effects on the hadronic B decay rates and their impact on direct CP violation. The color-suppressed neutral modes such as $B^0\to D^0\pi^0,\pi^0\pi^0,\rho^0\pi^0,K^0\pi^0$ can be substantially enhanced by long-distance rescattering effects. The direct CP-violating partial rate asymmetries in charmless B decays to $\pi\pi/\pi K$ and $\rho\pi$ are significantly affected by final-state rescattering and their signs are generally different from that predicted by the short-distance approach. For example, direct CP asymmetry in $B^0\to\rho^0\pi^0$ is increased to around 60% due to final state rescattering effects whereas the short-distance picture gives about 1%. Evidence of direct CP violation in the decay $\bar B^0\to K^-\pi^+$ is now established, while the combined BaBar and Belle measurements of $\bar B^0\to\rho^\pm\pi^\mp$ imply a $3.6\sigma$ direct CP asymmetry in the $\rho^+\pi^-$ mode. Our predictions for CP violation agree with experiment in both magnitude and sign, whereas the QCD factorization predictions seem to have some difficulty with the data. Current data on $\pi K$ modes seem to violate the isospin sum rule relation, suggesting the presence of electroweak penguin contributions. We have also investigated whether a large transverse polarization in $B\to \phi K^*$ can arise from the final-state rescattering of $D^{(*)}\bar D_s^{(*)}$ into $\phi K^*$.