[论文解读] Supersymmetry after the Higgs discovery and its LHC phenomenology

Sho Iwamoto|arXiv (Cornell University)|May 3, 2013

Particle physics theoretical and experimental studies参考文献 129被引用 3

一句话总结

该论文提出V-GMSB模型，即在规范介导的超对称（GMSB）基础上引入向量型物质（V-MSSM）的扩展，以调和126 GeV Higgs玻色子质量与μ子反常磁矩异常之间的矛盾。通过引入一个(10+10) SU(5)十重态向量型夸克与轻子，该模型通过圈修正提高了Higgs质量，使得停止夸克质量更轻（约1–2 TeV），并使CMSSM与GMSB方案重新具备可行性。关键成果是：126 GeV Higgs玻色子与2σ水平的μ子g−2异常可同时实现，且向量型夸克质量被限制在MV ≲1.2 TeV以内。

ABSTRACT

Under the minimal SUSY standard model (MSSM), the discrepancy in the muon g-2 suggests the SUSY particles are of order 100 GeV, which is also supported by discussions on the little hierarchy problem. However, the LHC experiments have found no scalar-quarks or gluinos in such mass range, and moreover, the Higgs boson mass of 126 GeV requires, within the MSSM framework, the scalar-top mass of order 1-10 TeV. This current status forces us to abandon the simplest supersymmetry-breaking frameworks of the CMSSM and the GMSB scenarios. The V-MSSM is investigated in this dissertation, which is proposed as an extension of the MSSM with a (10 + 10bar) pair of the SU(5) decuplets. In the framework the Higgs mass is increased by effect from the extra matters, and thus the 126 GeV is achieved with the scalar-top having a lighter mass. This fact resurrects the CMSSM and the GMSB scenarios. This dissertation examines the GMSB scenario under the V-MSSM; it is called V-GMSB scenario. It is shown that the V-GMSB has a potential to realize the 126 GeV mass of the Higgs boson with holding the explanation of the muon magnetic moment discrepancy, if the masses of the extra quarks are approximately less than 1.2 TeV. Constraints on the V-GMSB from the LHC experiments are discussed then; it is concluded that the gluino mass must be approximately heavier than 1.1 TeV, and that the extra quarks be heavier than 300-650 GeV depending on the decay branches of them. LHC prospects are briefly discussed. As the extra quarks are expected to be approximately less than 1.2 TeV, searches for the particles are of great interest at the 14 TeV LHC; constraints from the supersymmetry search, especially on the gluino mass, are expected to be much improved there. Therefore, it is expected that the fate of the V-GMSB is adjudicated at the court of the 14 TeV LHC.

研究动机与目标

• 在超对称模型中调和126 GeV Higgs玻色子质量与μ子反常磁矩（g−2）异常之间的张力。
• 使CMSSM与GMSB方案重新可行，这些方案此前因Higgs质量过高且缺乏超对称信号而被排除。
• 构建一个包含向量型物质的可行GMSB框架，既能解释Higgs质量，又能解释μ子g−2异常，且无需精细调节。
• 利用LHC超对称搜索与真空稳定性约束，对向量型夸克与轻子的质量尺度进行约束。
• 在Higgs玻色子发现后，为超对称理论提供一条与SU(5)大统一理论一致的可行发展路径。

提出的方法

• 通过引入一个(10+10)对SU(5)向量型物质多重态，提出MSSM的V-MSSM扩展。
• 计算向量型夸克与轻子对Higgs质量的辐射修正，将树图Higgs质量提升至126 GeV。
• 在向量型规范介导超对称性破缺（GMSB）框架中应用该机制，同时保持对味与CP问题的自由。
• 通过真空稳定性分析约束参数空间，特别是向量型质量尺度MV。
• 利用蒙特卡洛模拟与LHC搜索约束（如ATLAS b-夸克标记、带电粒子/中性子对产生）检验模型的物理可行性。
• 综合μ子g−2、Higgs质量与LHC搜索约束，识别参数空间中的可行区域。

实验结果

研究问题

• RQ1 在GMSB模型中，是否可在不需极重停止夸克的情况下实现126 GeV Higgs玻色子质量？
• RQ2 在同时满足126 GeV Higgs质量约束的前提下，μ子g−2异常是否可在GMSB框架中得到解释？
• RQ3 在LHC中，V-GMSB模型中的向量型夸克与轻子具有何种可观测特征？
• RQ4 在扩展的GMSB模型中，引入向量型物质如何影响真空稳定性？
• RQ5 在当前LHC数据与理论约束下，向量型夸克质量尺度MV的上限是多少？

主要发现

• V-GMSB模型成功实现了126 GeV Higgs玻色子质量，且停止夸克质量处于1–2 TeV范围内，解决了CMSSM与GMSB方案之间的张力。
• 在V-GMSB框架中，μ子g−2异常可在2σ水平内得到解释，而1σ水平的解释被LHC超对称搜索排除。
• 向量型夸克与轻子质量尺度MV被约束在1.2 TeV以下，意味着最轻的向量型夸克t′1质量小于≲1.1 TeV。
• 该模型预测，若向量型夸克质量在1.1 TeV范围内，14 TeV LHC运行（亮度约100 fb−1）将具备足够灵敏度以发现它们。
• V-GMSB模型为调和Higgs质量、μ子g−2与LHC约束提供了可行路径，同时保留了GMSB的理论优势。
• 真空稳定性约束进一步限制了参数空间，偏好MV的中等取值，确保电弱真空的长期稳定性。