What are effective a1 and a2 in two-body hadronic decays of D and B mesons?

Through a specific example of two-body color-favored charm decay, Ds+ → φπ+, the authors illustrate how an effective and complex (unitarized) a1, denoted by a1U,eff, may be defined such that it includes non factorized, annihilation and inelastic final-state interaction (f.s.i.) effects. The procedure can be generalized to color-suppressed processes to define an effective, and complex a2U,eff. The authors determine a1U,eff and, where relevant, a2U,eff for D → Κπ, Κρ, Κ*π,Ds+ → ηπ+, η'π+, ηρ+, η'ρ+, and for bO→D-π+ and D-ρ+ from the hadronic and semileptonic decay data