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arXiv 1508.01645hep-phhep-ex
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从Higgs耦合看标准模型的费米扩展

Fermionic extensions of the Standard Model in light of the Higgs couplings

Nicolas Bizot, Michele Frigerio

摘要:

随着希格斯玻色子性质的确定,对标准模型扩展的约束越来越紧。我们考虑所有可能的新费米子,可以耦合到希格斯玻色子,检查组多达四个手征多重态。我们用直接对撞机搜索、电弱精密测试和希格斯耦合的现有知识来对抗它们。重点是可能偏离非常大的质量和消失混合的去耦极限的情况,因为它们提供了最好的检测前景。我们确定外来的手征家庭,可能只从希格斯粒子接收质量,仍然与$hγγ$信号强度一致。标准模型和非手征费米子之间的混合$θ$导致希格斯耦合的$θ^2$阶偏差。在$Z$耦合的保管保护或倾斜参数的意外取消的情况下,混合可以大到$θ\sim 0.5$。我们还注意到一些有趣的影响,为更小的值的$θ$,特别是在轻子部门。我们的调查包括一些非常规的对矢量和马约拉纳费米子耦合通过希格斯粒子,这可能会导致一阶修正希格斯辐射耦合。我们挑出$hγγ$和$hgg$不受影响的参数区域,而$hγZ$信号强度被显著修改,在两种情况下比标准模型大几倍。大型强子对撞机的第二次运行将有效地测试大多数这些情况。

英文摘要:

As the Higgs boson properties settle, the constraints on the Standard Model extensions tighten. We consider all possible new fermions that can couple to the Higgs, inspecting sets of up to four chiral multiplets. We confront them with direct collider searches, electroweak precision tests, and current knowledge of the Higgs couplings. The focus is on scenarios that may depart from the decoupling limit of very large masses and vanishing mixing, as they offer the best prospects for detection. We identify exotic chiral families that may receive a mass from the Higgs only, still in agreement with the $hγγ$ signal strength. A mixing $θ$ between the Standard Model and non-chiral fermions induces order $θ^2$ deviations in the Higgs couplings. The mixing can be as large as $θ\sim 0.5$ in case of custodial protection of the $Z$ couplings or accidental cancellation in the oblique parameters. We also notice some intriguing effects for much smaller values of $θ$, especially in the lepton sector. Our survey includes a number of unconventional pairs of vector-like and Majorana fermions coupled through the Higgs, that may induce order one corrections to the Higgs radiative couplings. We single out the regions of parameters where $hγγ$ and $hgg$ are unaffected, while the $hγZ$ signal strength is significantly modified, turning a few times larger than in the Standard Model in two cases. The second run of the LHC will effectively test most of these scenarios.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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