希格斯玻色子的稀有衰变及相关问题的研究

After the 125GeV Higgs boson was discovered in Large Hadron Collider, Higgs physics has been concerned by particle physicists. It is necessary, both experimentally and theoretically, to identify the properties of this new particle, as well as to explore its origin and important roles in elementary particle physics. This project will focus on the rare decays of Higgs boson and some related issues. Since these decays are in general strongly suppressed or negiligible in the standard model, they may be very sensitive to the new physics scenarios beyond the standard model. Specifically, we will investigate branching ratios,decay spectrum, angular distributions and possible CP violation in rare decays; we will also analyze the standard model background, possible new physics effects, and the sensitivity of measurements in future high precision experiments for these decays. It is our purpose to carry out this project both to increase our undertstanding of Higgs physics, thus to test the standard model, and to probe the novel dynamics beyond the standard model.

随着大型强子对撞机LHC上质量为125GeV的Higgs玻色子的发现，Higgs物理的研究成为当前的一大热点。Higgs粒子的很多性质有待于实验上的进一步认定和精确测量，它的起源和更深层次的地位和作用也有待于实验和理论的进一步探讨。 本项目在追踪当前热点的同时，将针对Higgs的稀有衰变及相关问题展开研究，因为这些过程在标准模型中通常被强烈压低或者贡献可以忽略，所以它们对标准模型以外的新物理往往会比较敏感。具体来讲，我们将会系统研究这些稀有衰变过程的分支比、衰变谱、角分布及可能的CP破坏效应，分析这些衰变标准模型的背景、可能的新物理效应以及在将来的高精度实验中探测和检验的灵敏度，旨在通过这些具体问题的探讨，加深我们对Higgs玻色子各种性质的理解，检验标准模型和寻找标准模型以外的新物理。我们也会关注其他重要的相关问题。

本项目主要开展Higgs粒子和介子稀有衰变的研究，重点关注这些稀有衰变在标准模型中的贡献。稀有衰变来自标准模型的贡献往往会被压低，但在新物理模型中可能被增强。这样在寻找新物理的过程中，首要的任务就是要能够比较精确地计算这些稀有过程在标准模型中的背景。过去几年具体的研究工作包括：..1. eta-prime -> K pi 的弱衰变过程分支比计算及其中△I=1/2规则的研究；2. 轻味介子的invisible decay分支比计算和 螺旋性压低效应；3. B_s衰变到mu+mu-过程中来自标准模型双光子中间态long-distance的贡献；4. Higgs稀有衰变中三体和四体衰变过程的分析与计算。