Precision Measurements in Intermediate Energy Physics

中间能量物理的精密测量

• 批准号: 0758603
• 负责人: James Miller
• 金额: $ 136万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2014-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0758603&HistoricalAwards=false
• 关键词: Precision; Measurements; Intermediate; Energy; Physics

This project covers several precision measurements in particle physics. Precision measurements complement measurements at the highest energies, providing important constraints on the interpretation of data from the highest energies. The measurement of the muon lifetime, which gives the parameter G-Fermi and determines the strength of the weak force, will provide an improvement of this fundamental parameter by a factor of twenty better than it is presently known. This value will help constrain other parameters of the standard model of nuclear and particle physics. Our search for a permanent electric dipole moment of the neutron could obtain evidence for a new source of the violation of charge-parity (CP) symmetries, which at present has only been observed in the neutral K-meson and B-meson systems. While the asymmetry in the universe between matter (which we are made of) and antimatter could be partially explained by CP violation, the known source of CP violation is inadequate to explain the dominance of matter over antimatter. Finally, we are exploring the possibility of continuing our measurement of the magnetic moment of the muon, which is like a heavy electron. Our measurements at the Brookhaven National Laboratory obtained a value that is larger than that predicted by the standard model by 3.4 standard deviations, which indicates a 99% probability that this result cannot be explained by the standard model. We know that the standard model is incomplete, and many speculative extensions to it have predicted an effect consistent with our measurements. These projects provide significant educational and training opportunities for postdoctoral research associates and graduate students, as well as important roles in carrying out the research efforts.

这个项目涵盖了粒子物理中的几种精确测量。精确的测量补充了最高能量的测量，为解释来自最高能量的数据提供了重要的约束。介子寿命的测量给出了G-费米参数，并确定了弱力的强度，这将使这一基本参数改进20倍，比目前已知的要好。该值将有助于约束核物理和粒子物理标准模型的其他参数。我们对中子永久电偶极矩的探索可以为电荷宇称(CP)对称性的破坏提供新的来源的证据，目前这种对称性只在中性K介子和B介子系统中观察到。虽然宇宙中物质(构成我们的物质)和反物质之间的不对称性可以部分地用CP破坏来解释，但CP破坏的已知来源不足以解释物质对反物质的优势。最后，我们正在探索继续测量Muon的磁矩的可能性，Muon就像一个重电子。我们在布鲁克海文国家实验室的测量得到的值比标准模型预测的值大3.4个标准差，这表明这个结果不能用标准模型解释的可能性为99%。我们知道标准模型是不完整的，许多对它的推测性扩展已经预测到了与我们的测量结果一致的效果。这些项目为博士后研究助理和研究生提供了重要的教育和培训机会，并在开展研究工作中发挥了重要作用。