We investigate the recently reported tt¯ excess by the CMS Collaboration within the framework of conventional Two-Higgs-Doublet Models (2HDMs). Considering all four types (I, II, X, and Y), we perform a comprehensive parameter space scan using the best-fit values for a pseudoscalar boson A: MA=365 GeV, ΓA/MA=2%, and tan⁡β=1.28. Theoretical requirements and experimental constraints are systematically applied, including conditions from a bounded-below scalar potential, vacuum stability, unitarity, perturbativity, Flavor-Changing Neutral Currents (FCNCs), and direct searches at high-energy colliders. Our analysis shows that perturbativity imposes upper bounds of around 723 GeV on MH± and MH. FCNC constraints exclude all viable parameter space in Types II and Y, while a small region persists in Types I and X, but this region is ultimately ruled out by recent tt¯Z measurements by the ATLAS and CMS Collaborations at the LHC. We conclude that conventional 2HDMs alone cannot accommodate a pseudoscalar boson that explains the observed tt¯ excess within viable parameter space. However, incorporating toponium effects in the background fit could potentially alter this conclusion.

中文翻译：

---

在两个 Higgs-doublet 模型中，质量为 365 GeV 的伪标量能否解释 CMS [公式省略] 过量？


我们调查了 CMS 合作在传统双 Higgs-Doublet 模型 （2HDM） 框架内最近报告的 tt ̄ 过量。考虑到所有四种类型（I、II、X 和 Y），我们使用伪标量玻色子 A 的最佳拟合值进行全面的参数空间扫描：MA=365 GeV，ΓA/MA=2%，tanβ=1.28。系统地应用了理论要求和实验约束，包括来自有限下标量势、真空稳定性、幺正性、扰动率、风味变化中性电流 （FCNC） 的条件，以及对高能对撞机的直接搜索。我们的分析表明，微扰度对 MH± 和 MH 施加的上限约为 723 GeV。FCNC 约束排除了 II 型和 Y 型中所有可行的参数空间，而 I 型和 X 型中仍然存在一个小区域，但该区域最终被 LHC 的 ATLAS 和 CMS 合作最近的 tt ̄Z 测量排除了。我们得出结论，传统的 2HDM 本身无法容纳一个伪标量玻色子，该玻色子可以解释在可行参数空间内观察到的 tt ̄ 过量。然而，在背景拟合中加入地层效应可能会改变这一结论。