On Branching Ratios of $B_s$ Decays and the Search for New Physics in $B_s^0\to {\mu }^{+}{\mu }^{-}$

Abstract

The LHCb experiment has recently established a sizable width difference between the mass eigenstates of the $B_s$-meson system. This phenomenon leads to a subtle difference at the 10% level between the experimental branching ratios of $B_s$ decays extracted from time-integrated, untagged data samples and their theoretical counterparts. Measuring the corresponding effective $B_s$-decay lifetimes, both branching ratio concepts can be converted into each other. The rare decay $B_s^0\to {\mu }^{+}{\mu }^{-}$ 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.

Comments: 6 pages, invited talk at the 4th Workshop on Theory, Phenomenology and Experiments in Heavy Flavour Physics, Capri, Italy, 11-13 June 2012, to appear in the Proceedings