ACME III: Advanced Cold Molecule Electron Electric Dipole Moment Search

ACME III：高级冷分子电子电偶极矩搜索

• 批准号: 2136573
• 负责人: David DeMille
• 金额: $ 376.71万
• 依托单位: University of Chicago
• 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: 2021-06-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2136573&HistoricalAwards=false
• 关键词: ACME; III; Advanced; Cold; Molecule

The goal of this project is to search for a new fundamental property of the electron, one of the main constituents of matter and a charged component of all atoms. This new property, called an electric dipole moment, can be described as a slight bulge on an otherwise perfect sphere of charge. This seemingly abstruse feature may hold the key to one of the most fundamental mysteries of nature: why is everything in the universe made of matter rather than of antimatter? In accelerator laboratories, whenever energy is converted into particles (according to E=mc2), equal numbers of matter particles and antimatter particles are created. For example, the electron has a counterpart antimatter particle, the anti-electron, which has identical mass but opposite electric charge. Energy can be converted into an electron/anti-electron pair, and conversely an electron and anti-electron can annihilate each other and turn into energy. Just after the Big Bang, energy was converted into particles and anti-particles. Astronomical observations show that since then, essentially all the antimatter annihilated with matter--but a tiny bit of matter was left over. That small excess makes up all of the objects seen in the Universe today. The current framework that describes all known fundamental forces between elementary particles, known as the "Standard Model", cannot explain how this excess of matter survived. However, many mathematical theories have been devised that can explain this "matter-antimatter asymmetry", by positing new forces and particles not yet discovered in any experiment. These same new forces and particles also often lead, according to the same theories, to an electric dipole moment that is large enough to observe in the experiment supported here. Hence, this project is essentially seeking an answer to the question: how is it that matter was slightly preferred over anti-matter at some time in the past, resulting in the physical Universe seen today? In a general sense, this project also advances the range of techniques for precision measurement science, which in the past has led to unexpected breakthroughs in technology such as GPS (the Global Positioning System), new types of sensors, etc. The electric dipole moment (EDM), if it exists, must lie along the spin axis of the electron. In the presence of a nonzero EDM, an electric field will induce a torque on the electron, resulting in precession of the spin about the field. This spin precession angle is the experimental signal. The huge internal electric field of a polar molecule, ThO, is used to amplify this observable effect. The internal structure of ThO also suppresses possible systematic errors. A cryogenic molecular beam source that delivers an unprecedented high flux of molecules is used. Lasers and optical techniques put the ThO molecules in usable coherent superpositions and then probe the quantum interference that signals the electron's spin precession. Over the previous grant period, a version of these methods was used to make the most sensitive measurement of the electron's EDM. This result was consistent with a zero value for the EDM. However, many theories of what lies beyond the Standard Model of particle physics predict that, with improved sensitivity, detection of the EDM is likely. In this project, methods to greatly improve the sensitivity of the experiment will be introduced. These include focusing of the molecular beam and a use of longer interaction region to increase the time that a torque acts on the EDM. Improvements to reduce systematic errors observed in the previous experiment, such as the use of more carefully controlled magnetic fields and low-birefringence optical elements, will also be incorporated.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.

该项目的目的是寻找电子的新基本属性，这是物质的主要成分之一，也是所有原子的收费组成部分。这个称为电偶极力矩的新属性可以描述为在原本完美的电荷领域上的轻微凸起。这个看似深深的特征可能是自然界最基本的奥秘之一的钥匙：为什么宇宙中的一切都是由物质而不是反物质制成的？在加速器实验室中，每当能量转换为颗粒（根据E = MC2）时，就会产生相等数量的物质颗粒和反物质颗粒。例如，电子具有对应反物质粒子的抗电子粒子，该粒子具有相同的质量，但电荷相反。能量可以转换为电子/抗电子对，相反，电子和反电子可以互相消灭并变成能量。大爆炸之后，能量转化为颗粒和抗粒子。天文观察表明，从那时起，从本质上讲，所有用物质歼灭的反物质 - 但剩下的一小部分。那个小的多余构成了当今宇宙中看到的所有物体。当前描述基本颗粒（称为“标准模型”）之间所有已知基本力的框架无法解释物质过剩的生存方式。但是，已经设计了许多数学理论，可以通过提出任何实验中尚未发现的新力和粒子来解释这种“物质抗逆念不对称”。根据相同的理论，这些相同的新力和颗粒也经常引导到一个足够大的电动偶极矩，以便在此处支持的实验中观察到。因此，这个项目实质上是在寻求一个问题：过去某个时候，这与反物质有何偏爱，导致今天看到的物理宇宙？从一般意义上讲，该项目还推进了精确测量科学的技术范围，过去，这导致了技术的意外突破，例如GPS（全球定位系统），新型传感器等。电动偶极矩（EDM）（如果存在），则必须沿着电子的自旋轴进行。在存在非零EDM的情况下，电场将在电子上诱导扭矩，从而导致旋转围绕场的旋转。这种自旋进度角是实验信号。极性分子的巨大内部电场用于扩增这种可观察的效果。 THO的内部结构还抑制了可能的系统错误。使用的低温分子束来源使用了前所未有的高通量分子。激光器和光学技术将Tho分子放入可用的相干叠加中，然后探测信号的量子干扰，以表明电子的自旋进动。在上一个赠款期间，这些方法的版本用于对电子EDM进行最敏感的测量。该结果与EDM的零值一致。但是，许多超出标准粒子物理模型的理论预测，随着灵敏度的提高，可能会检测EDM。在这个项目中，将引入大大提高实验灵敏度的方法。这些包括聚焦分子束和使用较长的相互作用区域以增加扭矩在EDM上作用的时间。 还将合并以减少上一个实验中观察到的系统错误的改进，例如使用更仔细控制的磁场和低射流光学元素。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来支持的。

项目成果

High-sensitivity low-noise photodetector using a large-area silicon photomultiplier

使用大面积硅光电倍增管的高灵敏度低噪声光电探测器

• DOI: 10.1364/oe.475109
• 发表时间: 2023
• 期刊: Optics Express
• 影响因子: 3.8
• 作者: Masuda, Takahiko;Hiramoto, Ayami;Ang, Daniel G.;Meisenhelder, Cole;Panda, Cristian D.;Sasao, Noboru;Uetake, Satoshi;Wu, Xing;DeMille, David P.;Doyle, John M.
• 通讯作者: Doyle, John M.

Measurement of the H3Δ1 radiative lifetime in ThO

ThO 中 H3Î1 辐射寿命的测量

• DOI: 10.1103/physreva.106.022808
• 发表时间: 2022
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Ang, D. G.;Meisenhelder, C.;Panda, C. D.;Wu, X.;DeMille, D.;Doyle, J. M.;Gabrielse, G.
• 通讯作者: Gabrielse, G.

Measurement of the H3∆₁ Radiative Lifetime in ThO

ThO 中 H3→辐射寿命的测量

• 发表时间: 2022
• 期刊: ArXivorg
• 作者: Ang, D.G.;Meisenhelder, C.;Panda, C.D.;DeMille, D.;Doyle, J.M.;Gabrielse, G.
• 通讯作者: Gabrielse, G.

SiPM module for the ACME III electron EDM search

用于 ACME III 电子 EDM 搜索的 SiPM 模块

• DOI: 10.1016/j.nima.2022.167513
• 发表时间: 2023
• 期刊: Detectors and Associated Equipment
• 作者: Hiramoto, A.;Masuda, T.;Ang, D.G.;Meisenhelder, C.;Panda, C.;Sasao, N.;Uetake, S.;Wu, X.;Demille, D.;Doyle, J.M.
• 通讯作者: Doyle, J.M.

Electrostatic focusing of cold and heavy molecules for the ACME electron EDM search

用于 ACME 电子 EDM 搜索的冷分子和重分子静电聚焦

• DOI: 10.1088/1367-2630/ac8014
• 发表时间: 2022
• 期刊: New Journal of Physics
• 影响因子: 3.3
• 作者: Wu, X.;Hu, P.;Han, Z.;Ang, D. G.;Meisenhelder, C.;Gabrielse, G.;Doyle, J. M.;DeMille, D.
• 通讯作者: DeMille, D.