Precision Measurements of Flavor Changing Neutral Current Decays of B Mesons

我们测量了中性B介子衰变为KOsK+K-时的CP违反不对称性。它基于包含6.57亿个B-antiB对的数据样本。通过对具有KOsK+K-终态的BO衰变进行时间相关的Dalitz图分析，我们成功地测量了每个显著衰减幅度的CP违反相，并考虑了它们之间的干扰，解决了准两体时间相关CP分析中出现的弱相的双重模糊。在BO->φKOs衰变中发现了CP破坏的证据，其显著性为3.9σ，结果与标准模型的期望一致。我们还对改变味道的中性电流衰变B→Xsl+l-的分支分数进行了精确测量，其中Xs是包含s夸克的强子系统，l是电子或介子。这是迄今为止最精确的测量结果。

We measured CP violating asymmetries in the neutral B meson decaying to KOsK+K-. It was based on a data sample containing 657 million B-antiB pairs. By employing the time-dependent Dalitz plot analysis to the BO decays with KOsK+K- final state, we successfully measured the CP-violating phases in each significant decay amplitude taking into account the interferences between them and resolved two-fold ambiguity in the weak phases that arises in quasi-two-body time-dependent CP analyses. Evidence for CP violation at a significance of 3.9σ is found in the BO->φKOs decay and the result is consistent with the Standard Model expectation. We also made a precise measurement of the branching fraction for a flavor-changing neutral current decay B→Xsl+l-, where Xs is a hadronic system containing an s-quark and l is an electron or a muon. The results are the most precise measurements to date.