Nonfactorizable Effects in Charmless B Decays and B Meson Lifetimes

The nonleptonic two-body decays of mesons are conventionally evaluated under the factorization hypothesis. In the factorization approach, the decay amplitude is expressed in terms of factorizable hadronic matrix elements multiplied by some combinations of Wilson coefficient functions. To be more specific, the factorization hypothesis assumes that the 3-body hadronic matrix element 〈h1h2|O|M〉 for the decay M → h1h2 is approximated as th product of two matrix elements 〈h1|J1μ|0〉 and 〈h2|J 2 |M〉. However, it is known that this approach of naive factorization fails to describe the decays proceeding through the (class-I) color-suppressed internal W -emission diagrams, though it is at work for decay modes dominated by (class-II) external W -emission diagrams. This implies that it is necessary to take into account nonfactorizable contributions to the decay amplitude in order to render the color suppression of internal W -emission ineffective. Because there is only one single form factor involved in the class-I or class-II decay amplitude of B → PP, PV decays, the effects of nonfactorization can be lumped into the effective parameters a1 and a2: 1