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

我们对基础物理学的理解仍然有许多未解之谜，比如大爆炸后反物质的消失（当反物质与物质等量产生时），以及尚未发现的新粒子和力可能存在。某些室内规模的实验能够以补充大型粒子加速器研究的方式探索这些问题。这项资助下的研究旨在为这样一个小实验开发一种新方法，该实验将寻找原子核中电荷分布中的微小变形，即所谓的希夫矩，这种变形只能由携带力的新粒子引起，这种力可以解释宇宙物质-反物质不对称。这种新方法有望将这种变形的灵敏度提高到目前技术水平的1000倍，并将探测到某些粒子的存在，这些粒子的质量是当今世界上最大的粒子对撞机所能产生的任何粒子的数百倍。在这笔资助下，该小组的目标是执行实施这种方法所需的两个主要步骤：创造一种银原子的超冷气体，并开发一个连续的钫-223原子源。该基金将支持培养两名量子科学博士生；它还将使新的举措能够向芝加哥南部贫困的学生传达光学和量子物理学的兴奋和可及性。提出的新测量方法将使用一种光学捕获的极性分子223FrAg的超冷气体来寻找钫-223的希夫矩。这种方法同时结合了许多优势特性，几乎完全依赖于经过验证的技术。223Fr原子核呈梨形，其希夫矩提高了近1000倍。FrAg分子形成强烈的极性键，将可测量的信号提高了约10,000倍。Fr和Ag原子的简单结构使得它们以前可以被激光冷却和捕获。当被捕获在一起时，每个原子对可以不加热地组装成FrAg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，然后形成银的第一个BEC。由于223Fr的半衰期很短，研究小组将并行地开发出高通量、连续的223Fr原子源，这些原子源随后将用于对钫进行类似的步骤。为了在社区中实现更广泛的影响，该组织将把现有的SMART项目扩展到当地学校，部分方式是发起定期的“与科学家共进午餐”聚会。该奖项反映了美国国家科学基金会的法定使命，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。

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.