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arXiv 0908.3470hep-ph
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BR(B -> tau nu)的改进标准模型预测及其对新物理学的意义

An Improved Standard Model Prediction Of BR(B -> tau nu) And Its Implications For New Physics

UTfit Collaboration, M. Bona, M. Ciuchini, E. Franco, V. Lubicz, G. Martinelli, F. Parodi, M. Pierini, C. Schiavi, L. Silvestrini, V. Sordini, A. Stocchi, C. Tarantino, V. Vagnoni

摘要:

最近测得的B -> tau nu分支比允许通过探测新的重粒子的虚拟效应来测试标准模型,例如带电的希格斯玻色子。目前,测试的准确度受到BR(B -> τ nu)实验误差以及参数fB和|Vub|不确定性的限制。幺正三角拟合的冗余允许减少这些参数的误差,从而对标准模型进行更精确的测试。使用当前的实验输入,我们得到BR(B -> tau nu)_SM =(0.84 +- 0.11)x10^{-4},以与BR(B -> tau nu)_exp =(1.73 +- 0.34)x10^{-4}进行比较。标准模型的预测可以通过新物理效应在衰变振幅和幺正三角拟合中进行修改。我们将讨论如何解开的情况下,最小的味道违反在大tan β和通用环介导的新物理的两种可能的贡献。我们还考虑了两个特定的模型与最小的味道违反:第二类两个希格斯双重模型和最小超对称标准模型。

英文摘要:

The recently measured B -> tau nu branching ratio allows to test the Standard Model by probing virtual effects of new heavy particles, such as a charged Higgs boson. The accuracy of the test is currently limited by the experimental error on BR(B -> tau nu) and by the uncertainty on the parameters fB and |Vub|. The redundancy of the Unitarity Triangle fit allows to reduce the error on these parameters and thus to perform a more precise test of the Standard Model. Using the current experimental inputs, we obtain BR(B -> tau nu)_SM = (0.84 +- 0.11)x10^{-4}, to be compared with BR(B -> tau nu)_exp = (1.73 +- 0.34)x10^{-4}. The Standard Model prediction can be modified by New Physics effects in the decay amplitude as well as in the Unitarity Triangle fit. We discuss how to disentangle the two possible contributions in the case of minimal flavour violation at large tan beta and generic loop-mediated New Physics. We also consider two specific models with minimal flavour violation: the Type-II Two Higgs Doublet Model and the Minimal Supersymmetric Standard Model.

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