Towards Precision Measurements of Atomic Parity Violation Using Two-Pathway Coherent Control

使用两路相干控制精确测量原子宇称不守恒

• 批准号: 1607603
• 负责人: Daniel Elliott
• 金额: $ 58.7万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2019-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607603&HistoricalAwards=false
• 关键词: Towards; Precision; Measurements; Atomic; Parity

The four fundamental forces of the physical universe are gravitational, electromagnetic, weak (responsible for radioactive decay of particles), and strong (the binding force that holds the nuclei of atoms together). A great deal about these forces has been learned over the years, and a theoretical model that unifies and summarizes our understanding of three of these forces (electromagnetic, weak, and strong), known as the Standard Model, has been extremely precise in many of its predictions. There still persist, however, several very important open questions that cannot be explained within the Standard Model, or which fall outside the energy range in which the Standard Model is expected to be valid (such as conditions that existed during the very early stages of the universe). One of these is the existence and properties of dark matter: matter within our universe that we know exists (because of the slowing expansion of the universe), but which does not interact with regular matter in the universe through any means that we have been able to detect. Another is the possible existence of particles that are so massive that they have not yet been generated or observed at the large high-energy particle accelerators (such as the Large Hadron Collider in Switzerland). Yet a third area in which to search for physics beyond the Standard Model is to look for the indirect influence of the proposed extensions on extremely precise measurements of weak optical transitions in atoms. This is the focus of this research effort, which can help guide the answers to these fundamental questions about the universe.The principal investigator and his team will carry out new, higher-precision measurements of weak-force-induced transition amplitudes in atomic cesium. This atom was the focus of prior measurements by the group of Carl Wieman in Boulder in the 1990's, and these measurements of the parity violating amplitude are still the most precise reported for any element. There exists, however, a need to carry out atomic parity violation measurements at an even higher precision. Such a measurement will allow a more precise determination of the weak charge of the nucleus, and from that, an improved determination of the electroweak mixing angle at low momentum transfer. The energy dependence (or "running", as it is called) of this mixing angle, as measured through scattering measurements at various energies, places important constraints on conjectured massive bosons in theories that extend the standard model. These measurements also guide searches for dark matter candidates. Atomic parity violation measurements can also be used to determine the anapole moment of the atomic nucleus. This moment, resulting from weak interactions within the nucleus, provides the leading contribution to the nuclear spin dependence of the parity violating amplitude. To date, the Boulder group's measurement of the anapole moment of cesium is the only successful measurement in any element. Since this result is about twice as large as expected, and its magnitude is still not understood, there is a need for a new measurement to either verify or refute its magnitude. The goal of the present project is to return to cesium for a set of new, high-precision measurements that will address these goals. The principal investigator will apply a two-pathway coherent control technique to these measurements. One set of measurements are centered on the 6s - 7s transition, visited previously by Wieman, while a second set will examine similar effects in the ground state transition between hyperfine components.

物理宇宙的四个基本力是引力，电磁，弱（负责颗粒的放射性衰减）和强（将原子核核的结合力）结合在一起）。多年来，已经学到了很多关于这些力量的知识，并且一个理论模型统一并总结了我们对其中三种力（电磁，弱且强大）的理解，称为标准模型，在其许多预测中都非常精确。但是，仍然存在一些无法在标准模型中解释的几个非常重要的开放问题，或者超出了预期标准模型有效的能量范围（例如在宇宙早期阶段存在的条件）。其中之一是暗物质的存在和特性：我们知道存在的宇宙中的物质（由于宇宙的扩展放缓），但是通过我们能够检测到的任何方式，它们与宇宙中的常规物质没有相互作用。另一个是可能存在如此庞大的颗粒，以至于尚未在大型高能粒子加速器（例如瑞士的大型强子对撞机）上产生或观察到它们。 然而，在标准模型之外寻找物理的第三个领域是寻找拟议扩展对原子中弱光学转变的极为精确测量的间接影响。 这是这项研究工作的重点，它可以帮助指导有关宇宙的这些基本问题的答案。该原子是1990年代在博尔德（Boulder）的卡尔·维曼（Carl Wieman）组先前测量的重点，而违反平等振幅的这些测量仍然是任何元素的最精确报告。 但是，存在以更高的精度进行原子奇偶校验违规的测量。 这样的测量将允许对核的弱电荷进行更精确的确定，从而改善了低动量传递时的电动eak搅拌角的测定。 通过在各种能量的散射测量中测量的该混合角的能量依赖性（或称为“跑步”），对扩展标准模型的理论中的构想对大规模的大型玻色子进行了重要的约束。 这些测量还指导搜索候选暗物质的搜索。 原子均衡违规测量也可以用于确定原子核的Anapole矩。 这一刻是由于细胞核内的弱相互作用而产生的，为违反振幅的核旋转依赖性提供了主要贡献。 迄今为止，巨石组对剖腹的Anapole力矩的测量是任何元素中唯一成功的测量。 由于该结果大约是预期的两倍，而且其幅度仍然不明，因此需要进行新的测量来验证或反驳其幅度。 本项目的目的是返回库岛进行一系列新的高精度测量结果，以解决这些目标。首席研究员将对这些测量进行两条路线相干控制技术。 一组测量值集中在Wieman先前访问的6s -7s转变上，而第二组将检查在超精细组件之间的基态过渡中的类似效果。