Precision Measurements of Flavor Changing Neutral Current Decays of B Mesons

我们测量了衰变到KOSK+K-的中性B介子的CP破坏不对称性。它基于一个包含6.57亿对B-抗B对的数据样本。通过对具有KOSK+K-末态的BO衰变的含时Dalitz图分析，我们成功地测量了每个显著衰变振幅中的CP破坏位相，并考虑了它们之间的干扰，解决了在准两体含时CP分析中出现的弱相位的双重模糊性。在BO&GT；σ；φ的KOS衰变中发现了显著为3.9σ的CP破坏的证据，其结果与标准模型的预期一致。我们还精确测量了味变中性电流衰变B→xs1+L-的分支分数，其中xs是一个含有S夸克的强子系统，而L是一个电子或µ子。结果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.