Flavor symmetry for strong phases and determination of $\beta_s, \Delta\Gamma$ in $B_s \to J/\psi \phi$

Understand

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