On Branching Ratios of $B_s$ Decays and the Search for New Physics in $B^0_s\to μ^+μ^-$
Robert Fleischer
备注：
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
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 $B^0_s\to μ^+μ^-$ 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.
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利用LHCb实验，使用在$\sqrt s=8$收集的1.1\，fb $^{-1}$数据，对稀有衰变$B^0_s\rightarrow μ^+μ^-$和$B^0\rightarrow μ^+μ^-$进行搜索，TeV $ and 1.0\,fb$ ^{-1} $ of data collected at $ \sqrt s=7 $\,TeV. An excess of $ B^0_s \rightarrow μ^+μ^- $ candidates with respect to the background expectations is observed with a statistical significance of 3.5 standard deviations. A branching fraction of $ { \cal BR}（B^0_s \rightarrow μ^+μ^-）=（3.2^{+1.5}_{-1.2}）\times 10^{-9} $ is measured with an unbinned maximum likelihood fit. The measured branching fraction is in agreement with the expectation from the Standard Model. The observed n…
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