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arXiv 1905.08798hep-phastro-ph.COhep-ex
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一个预测性的$\mathbf{Z}_2$小破缺镜像孪生Higgs

A Predictive Mirror Twin Higgs with Small $\mathbf{Z}_2$ Breaking

Keisuke Harigaya, Robert McGehee, Hitoshi Murayama, Katelin Schutz

摘要:

孪生希格斯机制是解决小等级问题的一种方法,在这个问题中,在标准模型(SM)规范群下,最高的伙伴是中性的。最简单的镜像孪生希格斯(MTH)模型--其中一个$\mathbf{Z}_2$对称性复制了每个SM粒子--有太多的相对论自由度,与宇宙学观测不一致。我们证明,MTH模型可以有一个观测上可行的宇宙学,如果双质量谱导致双中微子去耦SM和双QCD相变之前。我们的解决方案要求双光子具有$\sim 20$ MeV的质量,并与SM光子动力学混合,以介导从双扇区到SM的熵转移。这个双光子可以被未来的实验发现或排除。此外,在这种情况下,早期宇宙中存在的残余孪生自由度将通过未来对宇宙微波背景的观测而被探测到。

英文摘要:

The twin Higgs mechanism is a solution to the little hierarchy problem in which the top partner is neutral under the Standard Model (SM) gauge group. The simplest mirror twin Higgs (MTH) model -- where a $\mathbf{Z}_2$ symmetry copies each SM particle -- has too many relativistic degrees of freedom to be consistent with cosmological observations. We demonstrate that MTH models can have an observationally viable cosmology if the twin mass spectrum leads to twin neutrino decoupling before the SM and twin QCD phase transitions. Our solution requires the twin photon to have a mass of $\sim 20$ MeV and kinetically mix with the SM photon to mediate entropy transfer from the twin sector to the SM. This twin photon can be robustly discovered or excluded by future experiments. Additionally, the residual twin degrees of freedom present in the early Universe in this scenario would be detectable by future observations of the cosmic microwave background.

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