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arXiv 1807.00593hep-phhep-ex
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上型特殊变体轴子模型中的μ介子g-2和罕见的top衰变

Muon g-2 and rare top decays in up-type specific variant axion models

Cheng-Wei Chiang, Michihisa Takeuchi, Po-Yan Tseng, Tsutomu T. Yanagida

备注：
35 pages, 9 figures
发表信息：
Phys. Rev. D 98, 095020 (2018)
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摘要：

不可见变体轴子模型（VAM）为强CP问题提供了一个非常有吸引力的解决方案，而没有畴壁问题。我们考虑向上型特定的变体轴子模型，并检查它们与μ子$g-2$异常的兼容性和来自轻子味普适性、几种味观测量和顶夸克测量的约束。我们发现，组合$χ^2$拟合有利于参数$m_A\sim 15$ GeV和$\tanβ\sim 40$，与X型2 HDM相同。此外，我们发现，只要混合角$ρ_u$足够小，与任何味道观测值都没有冲突。特别地，小的非零混合角$ρ_u \sim π/100$稍微受到所观察到的$B_s \to μμ$分支比的青睐。上特异性VAM预测了违反味道的顶级稀有衰变$t\to uA$，然后是$A \to ττ$，这将在LHC上提供确凿的证据。我们发现，目前的搜索$A$已经施加了一些限制的参数空间，但不敏感的最有趣的轻$m_A$区域。我们提出了一种有效的搜索策略，采用双头标记使用射流子结构信息，并证明它可以提高$BR(t \to uA)$的灵敏度，特别是在轻$m_A$区域。这个模型还预测了重希格斯玻色子（如$H \to t u$）的变味衰变，它会抑制$H \to ττ/μμ$的衰变。我们还研究了特定的VAM与μ子特定的轻子部门和向下型特定的VAM的有趣的替代方案。

英文摘要：

The invisible variant axion models (VAM's) offer a very attractive solution for the strong CP problem without the domain wall problem. We consider the up-type specific variant axion models and examine their compatibility with the muon $g-2$ anomaly and the constraints from lepton flavor universality, several flavor observables, and top quark measurements. We find that the combined $χ^2$ fit favors the parameters $m_A\sim 15$ GeV and $\tanβ\sim 40$, the same as the type-X 2HDM. Moreover, we find that there are no conflict with any flavor observables as long as the mixing angle $ρ_u$ is sufficiently small. In particular, a small nonzero mixing angle $ρ_u \sim π/100$ is slightly favored by the observed $B_s \to μμ$ branching ratio. The up-specific VAM predicts the flavor-violating top rare decay $t\to uA$ followed by $A \to ττ$, which would provide a smoking gun signature at the LHC. We show that current searches of $A$ already impose some constraints on the parameter space but are not sensitive to the most interesting light $m_A$ region. We propose an efficient search strategy that employs di-tau tagging using jet substructure information, and demonstrate that it can enhance the sensitivity on $BR(t \to uA)$, especially in the light $m_A$ region. This model also predicts the flavor-violating decay of heavy Higgs bosons, such as $H \to t u$, that would suppress the $H \to ττ/μμ$ decays. We also examine the up-specific VAM with the muon-specific lepton sector and the down-type specific VAM's as interesting alternative scenarios.

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