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arXiv 1802.01222hep-ph
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双Higgs模型中的衰变$A \to Zγγ$和$ϕ\to Zγγ$（$ϕ=h,H$）

Decays $A \to Zγγ$ and $ϕ\to Zγγ$ ($ϕ=h,H$) in two-Higgs doublet models

R. Sánchez-Vélez, G. Tavares-Velasco

备注：
24 pages, 13 figures, 2 tables
发表信息：
Phys. Rev. D 97, 095038 (2018)
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摘要：

在$CP$守恒的THDM框架内，计算了$CP$ -奇和$CP$ -偶标量玻色子$A\to Zγγ$和$ϕ\to Zγγ$（$ϕ=h,H$）的单圈衰变贡献，并利用盒图和可约费曼图导出了这些贡献.相应的分支比的行为，然后分析在II型THDM在一个区域的参数空间周围的对齐限制，仍然与实验数据一致。发现$A\to Zγγ$分支比仅在$m_A>m_H+m_Z$时是相关的，但在其它情况下是可忽略的。对于$m_A>600$ GeV和$t_β\simeq O(1)$，$BR(A\to Zγγ)$可以达到$10^{-5}-10^{-4}$数量级的值，但是当$t_β$增加到10时，它减少大约一个数量级。类似的行为之后是$H\to Zγγ$衰变，其仅在$m_H>m_A+m_Z$时具有不可忽略的分支比，并且对于$m_H>600$ GeV和$t_β\simeq O(1)$可以达到$10^{-4}-10^{-3}$的水平。我们还估计了I型THDM中这些罕见衰变的分支比，它们可以比II型THDM大一个数量级。就$h\to Zγγ$衰变而言，由于这个标量玻色子的性质必须与SM希格斯玻色子的性质几乎相同，所以$h\to Zγγ$分支比不会明显偏离SM预测，在那里它是可以忽略的小，在$10^{-9}$的数量级。这一结果与以前的计算是一致的。

英文摘要：

The one-loop contributions to the decays of the $CP$-odd and $CP$-even scalar bosons $A\to Zγγ$ and $ϕ\to Zγγ$ ($ϕ=h,H$) are calculated within the framework of $CP$-conserving THDMs, where they are induced by box and reducible Feynman diagrams. The behavior of the corresponding branching ratios are then analyzed within the type-II THDM in a region of the parameter space around the alignment limit and still consistent with experimental data. It is found that the $A\to Zγγ$ branching ratio is only relevant when $m_A>m_H+m_Z$, but it is negligible otherwise. For $m_A>600$ GeV and $t_β\simeq O(1)$, $BR(A\to Zγγ)$ can reach values of the order of $10^{-5}-10^{-4}$, but it decreases by about one order of magnitude as $t_β$ increases up to 10. A similar behavior is followed by the $H\to Zγγ$ decay, which only has a non-negligible branching ratio when $m_H>m_A+m_Z$ and can reach the level of $10^{-4}-10^{-3}$ for $m_H>600$ GeV and $t_β\simeq O(1)$. We also estimated the branching ratios of these rare decays in the type-I THDM, where they can be about one order of magnitude larger than in type-II THDM. As far as the $h\to Zγγ$ decay is concerned, since the properties of this scalar boson must be nearly identical to those of the SM Higgs boson, the $h\to Zγγ$ branching ratio does not deviates significantly from the SM prediction, where it is negligibly small, of the order of $10^{-9}$. This result is in agreement with previous calculations.

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