Puzzling out the Proton with Precision Scattering Experiments

通过精密散射实验解开质子的谜团

• 批准号: 2012114
• 负责人: Jan Bernauer
• 金额: $ 37.5万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2012114&HistoricalAwards=false
• 关键词: Puzzling; out; Proton; Precision; Scattering

Protons are one of the basic building blocks of matter and even 100 years after their discovery, they are still not fully understood. In fact, the precise radius of the proton is a puzzle and multiple measurements of this quantity do not all agree. A precise measurement of a proton’s radius is important because it determines the interaction with, and cross-section for scattering, other particles. The proton’s radius even affects the atomic spectroscopy of the hydrogen atom, which is tightly linked to the value of the Rydberg constant that has been so critical to the interpretation of all atomic spectra, because the electron and proton wave functions overlap and the radius is an important parameter in determining the amount of overlap. The research supported by this grant aims to resolve this “Proton Radius puzzle”. The Muon Proton Scattering Experiment (MUSE) at the Paul Scherrer Institute, Switzerland, will scatter a beam of electrons and muons off protons to measure the shape of the proton. The work of undergraduate and graduate students as well as postdoctoral researchers is central to these efforts, and they will gain knowledge and experience in precision nuclear physics experiments, modern detector and accelerator techniques, as well as in simulation and analysis algorithms. This international research effort will expose them to researchers from all over the world, fostering cultural exchange and give them opportunity to develop their communication and leadership skills.MUSE will make use of the worldwide unique beam available at the Paul Scherrer Institute to measure the lepton-proton cross section. It is the first measurement of muon-proton scattering that is precise enough to address the 4% effect at the heart of the proton radius puzzle. Through the measurement of muons of both charges, as well as electrons and positrons over a wide kinematic range, MUSE will provide crucial data to verify the existing e-p scattering results, test radiative corrections including two-photon-exchange by comparison of the two charges, and search for a violation of lepton universality by comparison of the two lepton families. Dr. Bernauer’s group will play a crucial role in the development of the software and the analysis of the data. Additional activities with the MAMI-A1 and MESA-MAGIX collaborations in Mainz, Germany, aim to reduce the leading systematic uncertainties on the proton electric form factor and will prepare a future experiment at MESA which will reduce the uncertainty of the magnetic form factor by two orders of magnitude. This will lead to an unprecedented precision on both the magnetic radius and the Zemach radius of the proton. The latter quantity is also accessible in spectroscopy and is, like the charge radius, a rare point of overlap between atomic and nuclear physics.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.

质子是物质的基本组成部分之一，即使在它们被发现100年后，人们仍然没有完全理解它们。事实上，质子的精确半径是一个谜，对这个量的多次测量并不都是一致的。精确测量质子的半径很重要，因为它决定了与其他粒子的相互作用和散射截面。质子的半径甚至影响氢原子的原子光谱，这与里德伯格常数的值密切相关，里德伯格常数对解释所有原子光谱非常关键，因为电子和质子波函数重叠，半径是确定重叠数量的重要参数。这项由该基金资助的研究旨在解开这个“质子半径之谜”。瑞士保罗·谢勒研究所的Muon质子散射实验(MUSE)将散射一束电子和质子上的Muon，以测量质子的形状。本科生和研究生以及博士后研究人员的工作是这些努力的核心，他们将获得精密核物理实验、现代探测器和加速器技术以及模拟和分析算法方面的知识和经验。这项国际研究工作将使他们接触到来自世界各地的研究人员，促进文化交流，并让他们有机会发展他们的沟通和领导技能。MUSE将利用保罗·谢勒研究所提供的全球独一无二的光束来测量轻子-质子截面。这是首个测量介子-质子散射的方法，其精确度足以解决质子半径之谜核心的4%效应。通过测量两种电荷的介子以及广泛运动范围内的电子和正电子，MUSE将提供关键数据来验证现有的e-p散射结果，通过比较两种电荷来测试包括双光子交换在内的辐射修正，并通过比较两个轻子族来寻找违反轻子普适性的情况。伯纳德博士的团队将在软件开发和数据分析方面发挥关键作用。与德国美因茨的Mami-A1和MESA-MAGIX合作开展的其他活动旨在减少质子电形状因数的主要系统不确定性，并将准备未来在MESA进行的一项实验，该实验将把磁形状因数的不确定性减少两个数量级。这将导致质子的磁场半径和泽马赫半径都达到前所未有的精度。后一个量也可以在光谱学中获得，并且像电荷半径一样，是原子物理和核物理之间罕见的重叠点。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

MUSE: The MUon Scattering Experiment

MUSE：MUon 散射实验

• DOI: 10.21468/scipostphysproc.5.023
• 发表时间: 2021
• 期刊: SciPost Physics Proceedings
• 作者: Cline, Ethan;Bernauer, Jan;Downie, Evangeline J.;Gilman, Ronald
• 通讯作者: Gilman, Ronald

Operation and characterization of a windowless gas jet target in high-intensity electron beams

高强度电子束中无窗气体射流靶的操作和表征

• DOI: 10.1016/j.nima.2021.165668
• 发表时间: 2021
• 期刊: Detectors and Associated Equipment
• 作者: Schlimme, B.S.;Aulenbacher, S.;Brand, P.;Littich, M.;Wang, Y.;Achenbach, P.;Ball, M.;Bernauer, J.C.;Biroth, M.;Bonaventura, D.
• 通讯作者: Bonaventura, D.

Polarization transfer in $$\varvec{e}^+p \rightarrow e^+ \varvec{p}$$ scattering using the Super BigBite Spectrometer

使用 Super BigBite 光谱仪进行 $$varvec{e}^ p ightarrow e^ varvec{p}$$ 散射中的偏振传输

• DOI: 10.1140/epja/s10050-021-00509-5
• 发表时间: 2021
• 期刊: The European Physical Journal A
• 作者: Puckett, A. J.;Bernauer, J. C.;Schmidt, A.
• 通讯作者: Schmidt, A.

Determination of two-photon exchange via $$e^+p/e^-p$$ scattering with CLAS12

通过 CLAS12 的 $$e^ p/e^-p$$ 散射确定双光子交换

• DOI: 10.1140/epja/s10050-021-00462-3
• 发表时间: 2021
• 期刊: The European Physical Journal A
• 作者: Bernauer, Jan C.;Burkert, Volker D.;Cline, Ethan;Schmidt, Axel;Sharabian, Youri
• 通讯作者: Sharabian, Youri

Direct TPE measurement via $$e^+p/e^-p$$ scattering at low $$\varepsilon $$ in Hall A

通过 A 厅低 $$varepsilon $$ 处的 $$e^ p/e^-p$$ 散射直接进行 TPE 测量

• DOI: 10.1140/epja/s10050-021-00597-3
• 发表时间: 2021
• 期刊: The European Physical Journal A
• 作者: Cline, Ethan;Bernauer, Jan C.;Schmidt, Axel
• 通讯作者: Schmidt, Axel