PM: Development Towards a Tabletop Experiment with Unprecedented Sensitivity to Hadronic CP Violation

PM：对强子 CP 破坏具有前所未有的敏感性的桌面实验的开发

• 批准号: 2208024
• 负责人: David DeMille
• 金额: $ 64.94万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2208024&HistoricalAwards=false
• 关键词: PM; Development; Towards; Tabletop; Experiment

Our understanding of fundamental physics still leaves many mysteries unsolved, such as the disappearance of antimatter after the big bang (when it was created in equal amounts with matter), and what yet-undiscovered new particles and forces may exist. Certain room-scale experiments are able to explore these questions in ways complementary to studies at large particle accelerators. The research under this grant aims to develop a new approach to such a small experiment, which would search for a tiny deformation in the distribution of electric charge in a nucleus, known as a Schiff Moment, that can only be caused by new particles carrying forces that could explain the cosmological matter-antimatter asymmetry. This new method promises to increase the sensitivity to this deformation by a factor of 1000 beyond the state of the art, and would probe the existence of certain particles hundreds of times heavier than any that could be produced at even the world's largest particle colliders today. Under this grant the group aims to perform two major steps needed to implement this method: create an ultracold gas of silver atoms, and develop a continuous source of francium-223 atoms. The grant will support training of two Ph.D. students in quantum science; it will also enable new initiatives to convey the excitement and accessibility of optical and quantum physics to underprivileged students on Chicago’s South Side. The proposed new measurement will use an optically-trapped, ultracold gas of the polar molecule 223FrAg to search for the Schiff Moment of francium-223. This approach combines many advantageous features at once, relying almost entirely on proven techniques. The 223Fr nucleus is pear-shaped, which enhances its Schiff Moment by a factor of nearly 1000. The FrAg molecule forms a strong polar bond that enhances the measurable signal by another factor of about 10,000. The simple structure of both Fr and Ag atoms has allowed them to be laser-cooled and trapped before. When trapped together, pairs of each atom can be assembled into FrAg molecules without heating, using methods applied to many other, similar atom pairs. The measurement precision relies on a long coherence time of a nuclear spin superposition, which has also been demonstrated in similar molecules under similar conditions. Creating this trapped sample of ultracold 223FrAg molecules will require forming a Bose-Einstein condensate (BEC) of both atoms, which in turn requires measuring the unknown ultracold scattering properties of both atoms. The group will make these measurements for silver atoms, then form the first BEC of silver. Because 223Fr has a short half-life, the group will in parallel develop a high-flux, continuous source of 223Fr atoms that will later be used to perform analogous steps for francium. To achieve the broader impacts in the community, the group will expand the existing SMART program of outreach to local schools, in part by initiating regular “lunch with a scientist” gatherings.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.

我们对基本物理的理解仍有许多未解之谜，例如反物质在大爆炸(当时它与物质的数量相等)后消失，以及可能存在哪些尚未发现的新粒子和新作用力。某些室内规模的实验能够以补充大粒子加速器研究的方式来探索这些问题。根据这项拨款进行的研究旨在开发一种新的方法来进行这样的小型实验，该实验将寻找原子核中电荷分布的微小变形，即所谓的希夫矩，这种变形只能由携带可以解释宇宙物质-反物质不对称性的新粒子产生。这种新方法有望将这种变形的灵敏度提高1000倍，超出最先进水平，并将探测某些粒子的存在，这些粒子的重量比当今世界上最大的粒子对撞机所产生的任何粒子都要重数百倍。根据这笔拨款，该小组的目标是执行实施这种方法所需的两个主要步骤：创建银原子的超冷气体，以及开发一个连续的法郎-223原子源。这笔拨款将支持两名量子科学博士生的培训；它还将使新的倡议成为可能，向芝加哥南区的贫困学生传达光学和量子物理的兴奋和可及性。拟议中的新测量将使用极性分子223FrAg的光学捕获的超冷气体来搜索Frcium-223的希夫矩。这种方法同时结合了许多优点，几乎完全依赖于经过验证的技术。223Fr核是梨形的，这使其希夫矩增加了近1000倍。FRAG分子形成了一个强大的极性键，将可测量的信号增强了约10,000倍。Fr和Ag原子的简单结构使它们以前可以被激光冷却和俘获。当被困在一起时，每个原子的对可以在不加热的情况下组装成碎片分子，使用的方法适用于许多其他类似的原子对。测量精度依赖于核自旋叠加的长相干时间，这一点在类似条件下的类似分子中也得到了证明。创建这个捕获的超冷223FrAg分子样本将需要形成两个原子的玻色-爱因斯坦凝聚体(BEC)，这反过来又需要测量两个原子未知的超冷散射特性。该小组将对银原子进行这些测量，然后形成第一个银的BEC。由于223Fr的半衰期很短，该小组将并行开发一种高通量、连续的223Fr原子源，稍后将用于执行类似的步骤来制造乳香。为了在社区中产生更广泛的影响，该组织将把现有的SMART计划扩展到当地学校，部分方式是发起定期的“与科学家共进午餐”聚会。这一奖项反映了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审查标准进行评估，被认为值得支持。