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arXiv 1503.08929hep-ph
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Z'质量极限与超对称性的自然性

Z' mass limits and the naturalness of supersymmetry

P. Athron, D. Harries, A. G. Williams

摘要:

125 GeV的希格斯玻色子的发现和超伴子质量下限的上升导致了人们对超对称模型现在被微调的担忧。大的停止质量,需要一个125 GeV的希格斯粒子,饲料到电弱对称性破缺条件通过重整化群方程迫使一个微调这些参数,以获得正确的电弱真空期望值。尽管如此,这种微调关键取决于我们对超对称破缺尺度的假设。同时,$U(1)$扩展为$μ$问题提供了最令人信服的解决方案,这也是一个自然性问题,并允许树级希格斯质量大大提高到$M_Z$以上。这些非常有动机的超对称模型预测了一种新的$Z'$玻色子,它可以在LHC中被发现,并且模型的自然性要求$Z'$玻色子的质量不应该超过TeV尺度太远。此外,这种微调出现在树的水平,使其不太依赖于假设的超对称性破缺机制。在这里,我们研究这种微调的几个$U(1)$超对称扩展的标准模型,并将其比较的情况下,在MSSM中,最直接的树级微调可以通过电荷质量限制进行探测。我们表明,未来的大型强子对撞机$Z'$搜索是非常重要的挑战,在这些模型中的最自然的情况。

英文摘要:

The discovery of a 125 GeV Higgs boson and rising lower bounds on the masses of superpartners have lead to concerns that supersymmetric models are now fine tuned. Large stop masses, required for a 125 GeV Higgs, feed into the electroweak symmetry breaking conditions through renormalisation group equations forcing one to fine tune these parameters to obtain the correct electroweak vacuum expectation value. Nonetheless this fine tuning depends crucially on our assumptions about the supersymmetry breaking scale. At the same time $U(1)$ extensions provide the most compelling solution to the $μ$-problem, which is also a naturalness issue, and allow the tree level Higgs mass to be raised substantially above $M_Z$. These very well motivated supersymmetric models predict a new $Z'$ boson which could be discovered at the LHC and the naturalness of the model requires that the $Z'$ boson mass should not be too far above the TeV scale. Moreover this fine tuning appears at the tree level, making it less dependent on assumptions about the supersymmetry breaking mechanism. Here we study this fine tuning for several $U(1)$ supersymmetric extensions of the Standard Model and compare it to the situation in the MSSM where the most direct tree level fine tuning can be probed through chargino mass limits. We show that future LHC $Z'$ searches are extremely important for challenging the most natural scenarios in these models.

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