缪介子反常磁矩的测量

Measurement of particle spin and magnetic moments have played a pivotal role in our understanding of the fundamental particles and forces of nature, and in the development of the Standard Model (SM).The muon anomalous magnetic momentum a_μ ≡ (g ? 2)/2 can be precisely measured and accurately computed within the SM and thus a comparison of experiment to theory is a sensitive test of the completeness of the theory and could provide hints for the new physics. Currently, there is a long-standing deviation of ~ 3.5 standard deviations from the predicted SM value, which might be an indication of non-SM physics.Precise measurement is crucial in understanding the deviation and will provide a benchmark discriminating between possible non-SM scenarios. The New Muon g-2 Experiment at Fermi National Accelerator Laboratory (Fermilab) is to measure a_μ with a factor of 4-5 improvement expected in the experimental precision, coupled with similar improvements expected in the prediction, it represents the world'latest and best development in this area. Shanghai Jiao Tong Unviersity has formally joined the Muon g-2 Collaboration representing the Chinese particle physics community. We have participated in the R&D of the calorimeter system, data acquisition system and the simulation tasks.The long-term goal is to collect 20 times more data and perform the world's best precise measurement of muon anomalous magnetic momentum. In this proposal, several key issues in the Muon g-2 experiment have been discussed and a detailed research plan has been presented. It will be one of the main research areas where SJTU particle physics group is going to make important contributions.

自旋以及磁矩是粒子的最基本物理量之一，对它们的精确测量一直都是粒子物理的最重要也是最基本的实验目标之一，这对研究粒子的内部结构以及物理特性都有着极其重要的物理意义。对缪介子磁矩的精确测量由于其对新物理的高度敏感性以及对非标准模型有着很强的制约和限定作用而尤为重要。前期的缪介子反常磁矩实验表明理论和实验值有大约3.5倍标准方差的差距，这急需新的更高精度实验来证实和解释，这也是发现TeV能级新物理的最佳途径之一。正在美国费米实验室开展的缪介子g-2实验将进行世界上精度最高的缪介子反常磁矩测量：精度预计提高4-5倍，数据量提高近20倍。上海交通大学已经代表中国加入到g-2国际合作组中，参与量能器和数据采集系统的设计和研发并将全程加入到数据采集和模拟、分析等一套完整的实验进程中。本计划书提出了交大g-2的研究规划和方案，这是交大粒子物理实验组的主要研究方向之一。

自旋和磁矩是粒子的最基本物理量之一，对它们的精确测量一直都是粒子物理的.最重要也是最基本的实验目标之一，这对研究粒子的内部结构以及物理特性都有.着极其重要的物理意义。对缪子磁矩的精确测量由于其对新物理的高度敏感性以.及对非标准模型有着很强的制约和限定作用而尤为重要。前期的缪介子反常磁矩.实验表明理论和实验值有大约3.5 倍标准方差的差距，这急需新的更高精度实验.来证实和解释，这也是发现TeV 能级新物理的最佳途径之一。正在美国费米实验.室开展的缪子g-2 实验正在进行世界上精度最高的缪子反常磁矩测量：测量精度.预计提高4倍，数据量提高近20 倍。上海交通大学于2012年代表中国加入到缪子.g-2 国际合作组中，作为主要合作单位参与了量能器及其数据采集系统的设计和.研发，在粒子束流测试等方面取得并发表了重要研究成果。目前交大研究团队.主要负责实验的数据产生和处理工作，同时研发和维护实验的总体数据库框架，.并将在接下来的数据分析工作中起到突出作用。