RUI: A Search for Long-Range Spin-Spin Interactions and Optical Forces in TlF

RUI：在 TlF 中寻找长程自旋-自旋相互作用和光学力

• 批准号: 1806297
• 负责人: Larry Hunter
• 金额: $ 48.06万
• 依托单位: Amherst College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1806297&HistoricalAwards=false
• 关键词: RUI; Search; Long; Range; Spin

Precision measurements of elementary particles' spins can provide new insight into the fundamental laws of nature. Elementary particles have an intrinsic property called spin which makes them act as if they are constantly rotating like mechanical tops. Just as tops precess in the presence of gravity, the spins of fundamental particles precess in a magnetic field. This precession is the basis of nuclear magnetic resonance which is the underlying physics used in the medical diagnostic known as magnetic resonance imaging (MRI). Recently developed precision optical techniques have allowed the study of interactions with particle spins with unprecedented fidelity. This project will use these precision techniques as tools to investigate the fundamental forces and symmetries of nature. At the most basic level, physicists' present understanding of nature is summarized by the "Standard Model" of particle physics. This model requires four fundamental forces (gravitational, electromagnetic, strong, and weak) to describe all of reality as it is presently known. In one experiment, the investigators will look for a new long-range force between particle spins that can't be described by the Standard Model. To optimize their search, they will measure the interaction of their laboratory spins with all of the aligned electron spins within the Earth. In their other experiment, the researchers hope eventually to see if the fundamental laws of nature might be asymmetric in time. This breaking of "time symmetry" can be studied by looking for the precession of a nuclear spin in an electric field. Here the experimental sensitivity is increased by using a beam of very cold molecules. Additional time asymmetry (beyond that which has already been observed) is believed to be necessary to explain the existence of our universe. Without time-reversal violation, our universe would have produced equal amounts of matter and anti-matter. Their mutual annihilation would not have allowed for the formation of galaxies, stars, planets and life. In 2013, the researchers created the first map of the electron-spin density within the Earth. These "geo-electrons" constitute the largest polarized spin source known. Precision measurement of spin-precession frequencies in laboratories at the surface of the Earth as a function of the magnetic-field direction, allows one to look for long-range spin-spin interactions (LRSSI) between the geo-electrons and the laboratory spins. In the first proposed experiment, a refined spin-precession apparatus will be constructed which is both well-calibrated and relatively immune to AC light effects. This should allow at least an order of magnitude improvement in the sensitivity of these LRSSI measurements. If an effect is seen it would suggest the existence of a new force of nature. In current models this force might be associated with an ultra-light vector meson, a "dark photon", the "unparticle", or torsion gravity. In the second proposed experiment, the researchers will continue their investigation of critical parameters that will ultimately determine the sensitivity of the thallium fluoride (TlF) electric-dipole moment (edm) experiment that is presently being constructed at Yale by the CeNTREX collaboration. Specifically, the researchers hope to continue to improve their measurements of optical cycling in TlF and to demonstrate that this cycling can be used to exert optical forces on TlF. These optical forces will be used to transversely cool a cryogenic molecular beam of TlF. This transverse cooling should increase the sensitivity of the TlF edm experiment by about an order of magnitude. With this additional sensitivity it is possible that a permanent nuclear edm will be discovered. If this edm is found, it would imply a violation of time symmetry and could help explain the existence of our matter-dominated universe.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.

对基本粒子自旋的精确测量可以提供对自然基本定律的新见解。基本粒子具有一种称为自旋的内在属性，这使得它们就像机械陀螺一样不断旋转。正如陀螺在重力作用下进动一样，基本粒子的自旋在磁场中进动。这种进动是核磁共振的基础，核磁共振是医学诊断中使用的基础物理学，即磁共振成像 (MRI)。最近开发的精密光学技术使得以前所未有的保真度研究粒子自旋的相互作用。该项目将使用这些精密技术作为工具来研究自然的基本力和对称性。在最基本的层面上，物理学家目前对自然的理解是通过粒子物理学的“标准模型”来概括的。该模型需要四种基本力（引力、电磁力、强力和弱力）来描述目前已知的所有现实。在一项实验中，研究人员将寻找标准模型无法描述的粒子自旋之间的新的远程力。为了优化他们的搜索，他们将测量实验室自旋与地球内所有对齐电子自旋的相互作用。在他们的另一个实验中，研究人员希望最终看看自然的基本定律是否可能在时间上不对称。这种“时间对称性”的破坏可以通过寻找电场中核自旋的进动来研究。在这里，通过使用非常冷的分子束来提高实验灵敏度。人们认为额外的时间不对称性（超出已经观察到的时间不对称性）对于解释我们宇宙的存在是必要的。如果没有时间反转破坏，我们的宇宙就会产生等量的物质和反物质。它们的相互湮灭就不可能形成星系、恒星、行星和生命。 2013年，研究人员绘制了第一张地球内电子自旋密度图。这些“地电子”构成了已知的最大的极化自旋源。在地球表面的实验室中精确测量自旋进动频率作为磁场方向的函数，使人们能够寻找地球电子与实验室自旋之间的长程自旋-自旋相互作用（LRSSI）。在第一个提出的实验中，将构建一个精致的自旋进动装置，该装置经过良好校准并且相对不受交流光效应的影响。这应该可以使这些 LRSSI 测量的灵敏度至少提高一个数量级。如果看到效果，则表明存在新的自然力。在当前模型中，这种力可能与超轻矢量介子、“暗光子”、“非粒子”或扭转引力有关。在第二个拟议的实验中，研究人员将继续研究关键参数，这些参数将最终确定氟化铊 (TlF) 电偶极矩 (edm) 实验的灵敏度，该实验目前由 CeNTREX 合作在耶鲁大学构建。具体来说，研究人员希望继续改进对 TlF 中光学循环的测量，并证明这种循环可用于对 TlF 施加光学力。这些光学力将用于横向冷却 TIF 低温分子束。这种横向冷却应将 TlF edm 实验的灵敏度提高大约一个数量级。有了这种额外的敏感性，就有可能发现永久的核电火花。如果发现这个 edm，则意味着时间对称性被破坏，并有助于解释我们以物质为主的宇宙的存在。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持审查标准。

项目成果

Toward a Free Precession Hg-Cs Co-magnetometer for Measurements of Long-Range Spin-Spin Interactions

用于测量长距离自旋-自旋相互作用的自由进动 Hg-Cs 共磁强计

• 发表时间: 2020
• 期刊: DAMOP 2020
• 作者: Clayburn, N.B.;Carlin, C.C.;Peck, S.K.;Hunter, L.R.
• 通讯作者: Hunter, L.R.

Optical Cycling of TlF

TlF 的光循环

• 发表时间: 2019
• 期刊: The Gordon Conference on Atomic Physics
• 作者: Clayburn, N.B.;Delaveron, J.H.;DeMille, D.;Hunter, L.R.
• 通讯作者: Hunter, L.R.

Improved Understanding of Optical Cycling in TlF

加深对 TlF 中光循环的理解

• 发表时间: 2022
• 期刊: Molecular and Optical Physics
• 作者: Clayburn, N.;Gabiyev, I.;Grasdijk, O.;Kastelic, J.;Timgren, O.;DeMille, D.;Hunter, L.
• 通讯作者: Hunter, L.

Improved Optical Cycling of TlF

改进的 TlF 光学循环

• 发表时间: 2021
• 期刊: DAMOP 2021
• 作者: Clayburn, N.B.;Cullen, M.;DeMille, D.;Hunter, L.R.
• 通讯作者: Hunter, L.R.