[论文解读] Exploring Extensions of the Scalar Sector of the Standard Model

Najimuddin Khan|arXiv (Cornell University)|Jan 9, 2017

Particle physics theoretical and experimental studies参考文献 3被引用 5

一句话总结

本博士论文通过SU(2)_L多重态研究标准模型标量场的扩展，聚焦于额外希格斯玻色子对电弱真空稳定性及暗物质可行性的影 响。研究表明，通过分析共振形状与相图，矢量玻色子散射过程可区分具有相似信号的模型，表明新标量场可在Z_2对称性下稳定电弱真空，并延长宇宙寿命。

ABSTRACT

In this thesis, various extensions of the scalar sector have been considered comprising of different ${SU(2)_L}$ multiplets. If the extended scalar sector participates in the electroweak symmetry breaking then these extra scalars need to couple with the known standard model particles. In this work, it has been shown that the vector boson scattering involving scalar boson exchanges provide a complimentary way to direct search methods to probe into the scalar sector. As different extended scalar sectors have similar types of scalar fields, e.g., an extra $CP$-even Higgs, charged Higgs etc., these new physics models can give rise to the similar types of experimental signatures. It is possible to distinguish between such models at various vector boson scattering processes by looking at the resonances. Also, the shapes of the resonances can provide further insight to the relevant parameter space of these models. As in the SM, the electroweak vacuum is metastable, it is important to explore if an extended scalar has an answer in its reserve. As the scalar weakly interacting massive scalar particles protected by $Z_2$ symmetry can serve as viable dark matter candidates, it is interesting to explore if they help prolong the lifetime of the Universe. The effective Higgs potential gets modified in the presence of these new extra scalars, improving the stability of electroweak vacuum. Such an exercise has been undertaken in various kinds of extended scalar sectors. In order to show the explicit dependence of the electroweak stability on different parameters of these extended sectors, various kinds of phase diagrams have been presented. Graphical demonstrations have been provided to illustrate how the confidence level, at which stability of electroweak vacuum is excluded, depends on such new physics parameters.

研究动机与目标

• 研究具有SU(2)_L多重态的扩展标量场对电弱真空稳定性的影响。
• 评估具有Z_2对称性的弱相互作用大质量标量粒子作为暗物质候选者的可行性。
• 确定新标量场如何修改有效希格斯势，并影响电弱真空的亚稳态性。
• 构建相图以说明真空稳定性对新物理参数的依赖关系。
• 探索矢量玻色子散射过程是否可区分具有相似实验信号的模型。

提出的方法

• 构建包含扩展SU(2)_L标量场中额外标量多重态的有效希格斯势。
• 应用跑动方程评估标量耦合的跑动及真空稳定性。
• 利用矢量玻色子散射振幅探测新物理，特别是通过散射过程中的共振结构。
• 生成相图以映射电弱真空保持稳定性的参数空间区域。
• 分析矢量玻色子散射中的共振形状，以区分具有相似末态的模型。
• 实施Z_2对称性以保护标量暗物质候选者，并评估其宇宙学影响。

实验结果

研究问题

• RQ1 具有SU(2)_L多重态的扩展标量场如何影响电弱真空的稳定性？
• RQ2 在何种参数区域内，新标量场可稳定电弱真空，且如何通过相图可视化？
• RQ3 矢量玻色子散射过程能否区分具有相似实验信号的模型，例如额外的CP偶性希格斯玻色子或带电希格斯玻色子？
• RQ4 Z_2保护的标量粒子在扩展标量模型中作为可行暗物质候选者的程度如何？
• RQ5 矢量玻色子散射中共振形状如何提供对底层模型参数的洞察？

主要发现

• 引入额外标量多重态会显著改变有效希格斯势，从而在多种参数区域内显著增强电弱真空的稳定性。
• 构建了相图以说明在不同新物理参数（如标量质量与耦合）下，电弱真空稳定性被排除的置信水平。
• 矢量玻色子散射中的共振形状被证明可作为区分具有相似末态模型（如存在额外CP偶性或带电希格斯玻色子的模型）的独特信号。
• 具有Z_2对称性的标量粒子被发现是可行的暗物质候选者，其存在可因稳定电弱真空而延长宇宙寿命。
• 本研究表明，矢量玻色子散射是直接搜寻的互补探测手段，尤其在识别与新标量态相关的共振结构方面具有优势。
• 明确的数值结果表明，当引入新标量场时，特别是在合适的耦合与质量尺度下，参数空间的广大区域中真空稳定性得以保持。