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
备注:
7 pages, 13 figures, 1 table. v2: added references and discussion of B -> D tau nu in the 2HDM. v3: added Bs->mumu in the 2HDM. Final version to appear in PLB
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.
Constraints on the rare tau decays from mu --> e gamma in the supersymmetric see-saw model
现在,所有族轻子数在自然界中都是不符合的,这已是一个确定的事实。在本文中,我们讨论了这一观察的影响,为未来的搜索罕见的τ衰变的超对称跷跷板模型。利用软项的两圈重整化群演化和Yukawa耦合,我们证明了稀有过程μ--> e γ的速率存在一个形式为BR(μ--> e γ)> C BR(τ--> μ γ)BR(τ--> e γ)的下界,其中C是一个依赖于超对称参数的常数.我们唯一的假设是在高能跷跷板参数之间不存在抵消。我们还讨论了这一约束的影响,为今后寻找罕见的tau衰变。特别是,对于mSUGRA参数空间的大区域,我们表明,目前的B工厂可以发现tau --> mu gamma或tau --> e gamma,但不能同时发现两者。
Implications of lepton flavor universality violations in B decays
目前对b->c tau nu和b->u tau nu跃迁的测量结果与标准模型对轻子味普适性的预测相差近4 σ。我们研究新的物理解释这种异常。一个有效场论分析表明,最小的味道违反模型不是首选的解释,但也尚未排除。考虑到一般的味违反,右-右矢量和右-左标量夸克流被确定为可行的候选者。我们讨论了两个希格斯双重模型,leptoquarks以及夸克和轻子复合明确的例子。最后,对LHC的搜索和未来的测量(超级)B-工厂的影响。
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