CP混合型Higgs粒子与轻子相互作用中味对称破缺的唯象研究

Higgs particle is the most important discovery of the fundamental particle physics in the past almost three decades, studies of its physical properties are the most essential tasks at the moment. The current experimental results indicate that there is a possibility of lepton flavor symmetry violation in the interactions between Higgs particle and leptons. Although conclusive experimental evidences have not yet been obtained, theoretical studies is already hot topic. On the other hand, the Higgs particle is also a promising candidate of CP violation sources. Given the above considerations, our studies will focus on the scenario in which both lepton flavor and CP symmetries are violated at the same time. Our project will adopt the method of effective field theory to analyze the possible physical phenomena, and gather up the clues to new physics. The contents include: 1) dependences of the Higgs decays on the parameters of lepton flavor symmetry violation and CP violation, as well as the angular distributions and spin correlations of the particles in final state; 2) electroweak dipole moments of leptons, lepton universality of electroweak coupling, and the phenomena of neutrino oscillation; 3) correlation properties and possible new physical models of the suspected abnormal signals. Our project is aim at obtaining the limits on the model parameters from current experimental results, illustrating the correlation properties of the suspected abnormal signals, and providing scientific criterions for exploring the possible physical mechanism of lepton flavor symmetry violation and CP violation.

Higgs粒子是近三十年来基本粒子物理学的一项重大发现，对其物理性质的研究是当前最重要的任务。目前的实验结果预示Higgs粒子与轻子的相互作用中可能存在味对称破缺。虽然还没有获得确凿的实验证据，但理论研究已成为热点课题。另一方面，Higgs粒子也是CP破缺源中较有前景的候选者。鉴于以上考虑，我们的研究将聚焦于这样一种设想，即轻子味对称和CP对称同时被破坏。本项目将采用有效场论的方法分析可能的物理现象，并理清新物理的线索。内容包括：1）Higgs粒子衰变对轻子味对称破缺和CP破缺参数的依赖特性，以及末态粒子的角分布和自旋关联；2）轻子电弱偶极矩，轻子电弱耦合一致性，以及中微子味振荡现象；3）疑似反常信号之间的关联特性和可能的新物理模型。本项目旨在获得目前实验结果对轻子味对称破缺和CP破缺参数的限制，揭示疑似反常信号之间的关联特性，为探索轻子味对称破缺和CP破缺的内在物理机制提供科学判据。

在本项目的资助下，我们发表了11篇论文。内容包括：1）研究了通过顶夸克对双轻子衰变道的自旋关联效应在正负电子对撞机上探测顶夸克Yukawa相互作用中的CP破缺效应的方法。提出了在正负电子撞机上对顶夸克CP破缺参数进行完备测量的分析方法。研究结果表明在Higgs粒子静止坐标系中CP观测量有更高对敏感度，且给出了新的CP观测量。此外，我们还研究了在强子对撞机LHC上探测顶夸克偶素的方法。提出了目前LHC上实验数据在顶夸克对双轻子衰变中观测到的偏离可能是顶夸克偶素形成导致的想法，并给出了在实验上提取顶夸克偶素实验证据的相关观测量。2）研究了一般情况下两体衰变中包含不可直接观测粒子（如中微子、暗物质）时，或者无法直接利用自旋关联效应时，如何利用单举观测量识别衰变道以及估计不可直接观测粒子的质量等物理参数的方法。3）本项目还开展了轻子混合以及非对易时空物理的相关研究。总体来讲，我们按时完成了本项目的主要研究内容。