On Branching Ratios of Bs Decays and the Search for New Physics in

The LHCb experiment has recently established a sizable width difference between the mass eigenstates of the Bs-meson system. This phenomenon leads to a subtle difference at the 10% level between the experimental branching ratios of Bs decays extracted from time-integrated, untagged data samples and their theoretical counterparts. Measuring the corresponding effective Bs-decay lifetimes, both branching ratio concepts can be converted into each other. The rare decay and the search for New Physics through this channel is also affected by this effect, which enhances the Standard-Model reference value of the branching ratio by O(10%), while the effective lifetime offers a new observable to search for physics beyond the Standard Model that is complementary to the branching ratio.