Precision Experiments to Study Fundamental Properties of Hadrons via Electromagnetic Probes at Jefferson Lab

杰斐逊实验室通过电磁探针研究强子基本性质的精密实验

• 批准号: 2111233
• 负责人: Ashot Gasparian
• 金额: $ 49万
• 依托单位: North Carolina Agricultural & Technical State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-15 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2111233&HistoricalAwards=false
• 关键词: Precision; Experiments; Study; Fundamental; Properties

With support from this award two experimental projects will be conducted at Jefferson Laboratory under the direct leadership of the PI and his group. The first project is the extension of an earlier experiment to measure the probability of a strongly interacting particle (the eta meson) decaying into two photons, which are light particles with very short wavelengths. The properties of eta mesons are very sensitive to fundamental symmetries and, most importantly, the spontaneous and explicit breaking of those symmetries. The effects of symmetry breaking plays critical roles in the formation of the visible matter in Universe. The second project is the preparation of an upgraded experiment to re-measure the proton charge radius by elastically scattering electrons from protons. The experiment is called PRad-II, and its goal is to determine the proton’s charge radius four times more precisely than the first PRad experiment, which the PI also led. The majority of students at North Carolina Agricultural & Technical State University are African American, and the PI will recruit students from that pool to work with him on these experiments. This award will support one undergraduate student, one graduate student, and one postdoctoral fellow who will be mentored and trained in highly technical skills that will prepare them for careers in STEM fields. With support from this award the PI and his group will measure the probability of eta decay to 2 photons with an uncertainty of 3%. That level of precision will significantly impact the eta-sector in the Particle Data Group’s (PDG) compilation by correcting the remaining eta-decay channels to other elementary particles. This will significantly improve our understanding of the light quark mass ratio in a direct and mostly model independent way. The second project supported by this award is the preparation of a new, upgraded experiment to re-measure the proton charge radius (PRad-II) experiment at Jefferson Lab. The result from the PI’s first experiment (PRad) agreed with the small radius from muonic hydrogen spectrometry measurements and played a critical role in the recent revision of the CODATA recommendation for the proton radius. During the grant period the PI and his group will develop, construct, test and install new detection systems to improve the results of the first experiment by a factor of four. This will be the most accurate measurement of the proton radius performed with the electron-proton scattering experiments. With this accuracy the PRad-II experiment will address the current difference between the PRad and other electron-proton scattering results.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在该奖项的支持下，两个实验项目将在PI及其团队的直接领导下在杰斐逊实验室进行。 第一个项目是早期实验的延伸，测量强相互作用粒子（eta介子）衰变为两个光子的概率，光子是波长很短的光粒子。η介子的性质对基本对称性非常敏感，最重要的是，这些对称性的自发和显式破缺。 对称性破缺效应对宇宙中可见物质的形成起着至关重要的作用。 第二个项目是准备一个升级实验，通过质子弹性散射电子来重新测量质子电荷半径。 该实验被称为PRad-II，其目标是确定质子的电荷半径比PI领导的第一个PRad实验精确四倍。北卡罗来纳州农业技术州立大学的大部分学生都是非洲裔美国人，PI将从这个群体中招募学生与他一起进行这些实验。 该奖项将支持一名本科生，一名研究生和一名博士后研究员，他们将接受高技术技能的指导和培训，为他们在STEM领域的职业生涯做好准备。 在该奖项的支持下，PI和他的团队将测量eta衰减到2个光子的概率，不确定度为3%。 这种精度水平将通过将剩余的η衰变通道校正为其他基本粒子来显著影响粒子数据组（PDG）编译中的η扇区。 这将以直接且基本上独立于模型的方式显着提高我们对轻夸克质量比的理解。该奖项支持的第二个项目是准备一个新的升级实验，以重新测量杰斐逊实验室的质子电荷半径（PRad-II）实验。 PI的第一个实验（PRad）的结果与μ子氢光谱测量的小半径一致，并在最近修订的CODATA质子半径建议中发挥了关键作用。在资助期间，PI和他的团队将开发、构建、测试和安装新的检测系统，以将第一次实验的结果提高四倍。这将是用电子-质子散射实验进行的质子半径的最准确的测量。PRad-II实验将解决PRad和其他电子-质子散射结果之间的差异。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。