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arXiv 1102.4347hep-phhep-ex
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最小味破坏模型中t --> b-W衰变与B_q介子混合的相互作用

Interplay of t --> b W Decay and B_q Meson Mixing in Minimal Flavor Violating Models

Jure Drobnak, Svjetlana Fajfer, Jernej F. Kamenik

摘要:

在强子对撞机上对顶夸克衰变性质的精确测量为检验标准模型提供了有趣的新可能性。与此同时,最近关于B_d和B_s系统CP破坏的有趣实验结果也激发了许多超越标准模型的物理研究。我们在基于最小味破坏假设的模型独立方法中研究了作为B_{d,s} -棒B_{d,s}振荡中新效应的可能来源的异常t W d_j相互作用.通过将我们的有效算符与描述B_{d,s}介子混合的低能有效拉格朗日量匹配,并将其向下演化到B质量尺度,我们得到了弱尺度下反常t W d j相互作用的优选范围.然后将这些值与先前考虑的来自稀有辐射B -> X_s γ衰变的约束进行比较。最后,我们重新考虑了t --> b W衰变中的关联效应,发现W螺旋度分数F_{L,+}可以分别偏离它们的标准模型值15%和30%。特别是F_L的偏差,可以达到LHC预期的精度测量水平。

英文摘要:

Precise measurements of the top quark decay properties at hadron colliders offer interesting new possibilities of testing the standard model. At the same time, recent intriguing experimental results concerning CP violation in the B_d and B_s systems have stimulated many studies of physics beyond the standard model. We investigate anomalous t W d_j interactions as a possible source of new effects in B_{d,s} - bar B_{d,s} oscillations within a model independent approach based on the assumptions of Minimal Flavor Violation. After matching our effective operators onto the low-energy effective Lagrangian describing B_{d,s} meson mixing and evolving it down to the B-mass scale, we extract the preferred ranges of the anomalous t W d_j interactions at the weak scale. These values are then compared to previously considered constraints coming from the rare radiative B --> X_s gamma decay. Finally, we reconsider the associated effects in the t --> b W decays and find that the W helicity fractions F_{L,+} can deviate by as much as 15%, 30% from their standard model values, respectively. The deviations in F_L in particular, can reach the level of expected precision measurements at the LHC.

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