Flavor symmetry for strong phases and determination of $β_s, ΔΓ$ in $B_s \to J/ψϕ$

Abstract

Studies of angular and time distributions and CP-violating observables in $B_s\to J/ψϕ$ 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 $B_s \to J/ψϕ$ and $B^0 \to J/ψK^{*0}$ 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 $B^0 \to J/ψK^{*0}$ in the analysis of $B_s \to J/ψϕ$ 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.