Effective lifetimes of Bs decays and their constraints on the Bs0-(B)over-bars0 mixing parameters

Measurements of the effective lifetimes of B-s-meson decays, which only require untagged rate analyses, allow us to probe the width difference Delta Gamma(s) and the CP-violating phase phi(s) of B-s(0)-(B) over bar (0)(s) mixing. We point out that the dependence of the effective lifetime on non-linear terms in Delta Gamma(s) allows for a determination of phi(s) and Delta Gamma(s) given a pair of Bs decays into CP-even and CP-odd final states. Using recent lifetime measurements of B-s(0). K+K- and B-s(0) -> J/psi f(0) (980) decays, we illustrate this method and show how it complements the constraints in the phi(s)-Delta Gamma(s) plane from other observables.