Final state interactions in hadronic B decays

By Hai-Yang Cheng, C. Chua, A. Soni. 2004

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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{sup 0}{yields}D{sup 0}{pi}{sup 0},{pi}{sup 0}{pi}{sup 0},{rho}{sup 0}{pi}{sup 0},K{sup 0}{pi}{sup 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 (SD) approach. For example, direct CP asymmetry in B{sup 0}{yields}{rho}{sup 0}{pi}{sup 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 B{sup 0}{yields}K{sup -}{pi}{sup +} is now established, while the combined BABAR and Belle measurements of B{sup 0}{yields}{rho}{sup {+-}}{pi}{sup {+-}} imply a 3.6{sigma} direct CP asymmetry in the {rho}{sup +}{pi}{sup -} mode. Our predictions for CP violation agree with experiment in both magnitude and sign, whereas the QCD factorization predictions (especially for {rho}{sup +}{pi}{sup -}) seem to have some difficulty with the data.more » Direct CP violation in the decay B{sup -}{yields}{pi}{sup -}{pi}{sup 0} is very small ((less-or-similar sign)1%) in the standard model even after the inclusion of FSIs. Its measurement will provide a nice way to search for new physics as in the standard model QCD penguins cannot contribute (except by isospin violation). 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{yields}{phi}K* can arise from the final-state rescattering of D{sup (}*{sup )}D{sub s}{sup (}*{sup )} into {phi}K*. While the longitudinal polarization fraction can be reduced significantly from short-distance predictions due to such FSI effects, no sizable perpendicular polarization is found owing mainly to the large cancellations occurring in the processes B{yields}D{sub s}*D{yields}{phi}K* and B{yields}D{sub s}D*{yields}{phi}K*, and this can be understood as a consequence of CP and SU(3) [CPS] symmetry. To fully account for the polarization anomaly (especially the perpendicular polarization) observed in B{yields}{phi}K*, FSI from other states or other mechanism, e.g., the penguin-induced annihilation, may have to be invoked. Our conclusion is that the small value of the longitudinal polarization in VV modes cannot be regarded as a clean signal for new physics.« less

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/17954318c6067813036cdc01168f77c8a337b4f6