发表机构
The Open University of Japan（日本开放大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文以LHC的$t\bar{t}$超出事例为启发，在顶夸克友好型III型2HDM中研究电弱重子产生，对比显式与过渡CP破坏情景，发现显式CP破坏为方案依赖可能性，未找到可行的过渡CP破坏分支。
AI 中文摘要
最近，CMS合作组和ATLAS合作组在顶夸克-反顶夸克对的不变质量分布的产生阈值附近观测到了一个增强事例。可能的解释包括赝标量顶夸克偶素准束缚态，以及与顶夸克偶素共存或混合的额外基本赝标量。受后一种解释的启发，我们将该额外赝标量确定为顶夸克友好型III型双希格斯二重态模型（2HDM）中的CP-奇希格斯玻色子。从电弱重子产生的角度来看，这种可能性也很有意义：扩展的标量部分可以支持强一阶电弱相变，而额外的顶夸克汤川相互作用可以通过泡壁背景提供CP破坏源。因此，我们研究受$t\bar{t}$阈值增强启发的同一参数区域是否也能解释观测到的宇宙重子不对称性（BAU）。我们比较了两种不同CP破坏起源的情景：在显式CP破坏情景中，一个复相位被引入额外的顶夸克汤川耦合$\rho_{tt}$；在过渡CP破坏（TCPV）情景中，通过有限温度效应在泡壁内部动态产生CP-奇场组态。在当前的单圈处理中，显式CP破坏仍是依赖于方案的可能性，而未发现可行的过渡CP破坏分支。此外，我们还讨论了这两种情景的物理差异和可行性。
英文摘要
The CMS and ATLAS Collaborations have reported a $t\bar{t}$ threshold enhancement possibly involving a pseudoscalar toponium quasi-bound state and an elementary pseudoscalar. Identifying the elementary pseudoscalar with the CP-odd Higgs boson, we investigate electroweak baryogenesis in the top-philic Type-III two-Higgs-doublet model (2HDM), whose scalar sector may support a strong first-order electroweak phase transition. We compare two scenarios: explicit CP violation and transitional CP violation (TCPV). In the first, a complex additional top-quark Yukawa coupling induces a spatially varying phase of the top-quark mass across the bubble wall. This generates a chiral asymmetry that electroweak sphalerons convert into baryon asymmetry. In TCPV, CP symmetry would be broken inside the bubble wall but preserved in the vacuum in the absence of explicit CP violation. A small explicit CP-violating bias would favor one of the otherwise CP-conjugate wall configurations, avoiding exact cancellation of the generated baryon asymmetry. This could allow baryogenesis without large explicit CP violation, potentially alleviating electric dipole moment constraints. Combining a one-loop finite-temperature analysis of bubble nucleation with transport calculations, we find that electroweak baryogenesis with explicit CP violation remains possible, although this conclusion depends on the thermal-resummation schemes. No viable TCPV solution is found in the parameter regions explored.
Comments36 pages and 5 Figures, v2, we revised the attached figures, added information on the numerical calculations, added references, and revised some of the wording
