arXiv 1302.52622013-02hep-ph

在发现希格斯粒子后修正超对称模型中的EW标度

Fixing the EW scale in supersymmetric models after the Higgs discovery

D. M. Ghilencea

备注：: 18 pages; (v4: added text in Conclusions)
DOI：: 10.1016/j.nuclphysb.2013.07.024

摘要：

TeV尺度的超对称性最初是为了解决层次问题而引入的，因此在量子修正的情况下固定了电弱（EW）尺度。检验超对称模型的数值方法通常会报告一个很好的似然L（或chi^2=-2ln L）来拟合数据{ \it包括} EW尺度本身（m_Z^0），同时进行{ \it}大的微调，即在超对称参数的小变化下，该尺度的大变化。我们认为，这是不一致的，我们确定这个问题的根源。我们的主张是，拟合此类模型中通常报告的数据的可能性（或chi 2）并不能解释固定EW尺度的chi 2成本。当实现此约束时，似然（或chi ^2）会收到一个显著的校正（delta_chi ^2），该校正将超对称模型的当前数据拟合。我们估计这种校正的模型：约束MSSM（CMSSM），模型与非普适gaugino质量（NUGM）或希格斯软质量（NUHM 1，NUHM 2），NMSSM和一般NMSSM（GNMSSM）。对于质量为m_h \approx 126 GeV的希格斯粒子，我们发现在这些模型中，（delta_chi ^2）/ndf> 1.5（GNMSSM近似为1），这违反了在拟合EW尺度本身以外的观测值（ndf=自由度）之前就已经存在的良好拟合的通常条件（总chi ^2/ndf近似为1）。这对超对称模型有（负面）影响，如果人们仍然忠于超对称模型的原始目标，建议未来的数据适当地考虑这种影响。由于我们的计算得出的delta_chi ^2的表达式依赖于一种熟悉的微调措施，因此可以得出结论，EW微调是拟合包含EW尺度（m_Z^0）的数据的可能性的固有部分。

英文摘要：

TeV-scale supersymmetry was originally introduced to solve the hierarchy problem and therefore fix the electroweak (EW) scale in the presence of quantum corrections. Numerical methods testing the SUSY models often report a good likelihood L (or chi^2=-2ln L) to fit the data {\it including} the EW scale itself (m_Z^0) with a {\it simultaneously} large fine-tuning i.e. a large variation of this scale under a small variation of the SUSY parameters. We argue that this is inconsistent and we identify the origin of this problem. Our claim is that the likelihood (or chi^2) to fit the data that is usually reported in such models does not account for the chi^2 cost of fixing the EW scale. When this constraint is implemented, the likelihood (or chi^2) receives a significant correction (delta_chi^2) that worsens the current data fits of SUSY models. We estimate this correction for the models: constrained MSSM (CMSSM), models with non-universal gaugino masses (NUGM) or higgs soft masses (NUHM1, NUHM2), the NMSSM and the general NMSSM (GNMSSM). For a higgs mass m_h\approx 126 GeV, one finds that in these models (delta_chi^2)/ndf> 1.5 (approx 1 for GNMSSM), which violates the usual condition of a good fit (total chi^2/ndf approx 1) already before fitting observables other than the EW scale itself (ndf=number of degrees of freedom). This has (negative) implications for SUSY models and it is suggested that future data fits properly account for this effect, if one remains true to the original goal of SUSY. Since the expression of delta_chi^2 that emerges from our calculation depends on a familiar measure of fine-tuning, one concludes that EW fine-tuning is an intrinsic part of the likelihood to fit the data that includes the EW scale (m_Z^0).

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英文摘要：

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