RUI: Calculation of the Positronium Hyperfine Interval

RUI：正电子超精细间隔的计算

• 批准号: 1404268
• 负责人: Gregory Adkins
• 金额: $ 18万
• 依托单位: Franklin and Marshall College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1404268&HistoricalAwards=false
• 关键词: RUI; Calculation; Positronium; Hyperfine; Interval

Positronium is the bound state of the electron and its antiparticle, the positron. As such, it forms an "exotic atom", similar in many ways to the traditional simple atoms such as hydrogen and helium, but different because of its unique composition and because of its tendency to annihilate, transforming into pure electromagnetic energy in the form of high-energy photons. Many properties of positronium, such as energy level differences and lifetimes, are accessible to high-precision experiments. Positronium properties can also be calculated theoretically to high precision. Consequently, positronium is an ideal system for testing the limits of electromagnetic bound state physics. The positronium hyperfine splitting--the interval between the spin-1 and spin-0 variants of the lowest energy state--is of prime interest because there is a long-standing difference (of about four times the experimental uncertainty) between theory and experiment for this splitting. The current proposal is to calculate the positronium hyperfine interval to a higher level. When complete, the result of this work will help to resolve or sharpen the positronium hyperfine discrepancy. This theoretical work is timely because two experimental groups, based at the University of California, Riverside and at the University of Tokyo, are developing improved experimental measurements of the hyperfine interval. The combination of improved experimental results and higher precision theory will work together to give bound-state Quantum Electrodynamics (QED) one of its most stringent tests to date. An important aspect of this project will be the training of undergraduate student collaborators in the techniques and processes of scientific investigation in this field. The overall project involves a number of distinct parts that will make ideal projects for small teams of students. The students will cooperate in all aspects of the work including the development of calculational techniques and tools, the calculations themselves, presentation at scientific meetings, and publication. Positronium properties will be calculated theoretically to high precision using the methods of bound-state Quantum Electrodynamics (QED) because strong and weak interaction effects are negligible. The positronium hyperfine interval will be calculated to a higher level of precision than heretofore by completing all three-loop corrections to the hyperfine interval. This will require an application of effective field theory methods, specifically Non-Relativistic QED (NRQED), at the three-loop order. When complete, the result of this work will help to resolve or sharpen the positronium hyperfine discrepancy.

正电子是电子及其反粒子的结合状态，即正电子。因此，它形成了“异国原子”，在许多方面类似于传统的简单原子，例如氢和氦气，但由于其独特的成分和倾向于歼灭，以高增强光子的形式转化为纯电磁能。正电子的许多特性，例如能级差异和寿命，可以进行高精度实验。 正电子特性也可以从理论上计算为高精度。因此，正电子是测试电磁结合状态物理学极限的理想系统。优质能量状态的旋转-1和自旋-0变体之间的间隔是主要感兴趣的，因为这种分裂的理论与实验之间存在长期差异（大约是实验不确定性的四倍）。当前的建议是将正电子超精细时间间隔计算到更高的水平。完成后，这项工作的结果将有助于解决或升起普通超精致的差异。这项理论工作是及时的，因为在加利福尼亚大学，里弗赛德大学和东京大学的两个实验组正在开发超精细间隔的改进的实验测量。改进的实验结果和更高的精度理论的结合将共同起作用，以使结合状态量子电动力学（QED）迄今为止最严格的测试之一。该项目的一个重要方面是在该领域的科学研究技术和过程中培训本科生合作者。 整个项目涉及许多不同的部分，这些部分将为小型学生团队提供理想的项目。学生将在工作的各个方面合作，包括开发计算技术和工具，计算本身，科学会议上的演讲以及出版。 由于强和弱相互作用的效应可以忽略不计，因此理论上将在理论上计算出正电子性能。通过完成所有三循环校正，将对超细校正进行高精细间隔，将计算出比迄今为止更高的精度。这将需要在三环秩序上应用有效的现场理论方法，特别是非权威性QED（NRQED）。完成后，这项工作的结果将有助于解决或升起普通超精致的差异。