Flavor symmetry for strong phases and determination of βs,ΔΓ in Bs→J/ψϕ

Studies of angular and time distributions and CP-violating observables in Bs→J/ψϕ decays yield a space of parameters which can be considerably reduced if relative strong phases among different amplitudes are specified. We show that the relations between Bs→J/ψϕ and B0→J/ψK∗0 amplitudes given by flavor symmetry [actually U(3) rather than SU(3)] are likely to be quite reliable, and hence the use of strong phases from B0→J/ψK∗0 in the analysis of Bs→J/ψϕ is justified. We point out the potential advantage of using helicity angles over transversity angles, and comment on a way to measure a sizable CP-violating phase independent of strong phases.