RUI: A Hg-Cs LLI Search and the Prospects for Laser Cooling TlF

我们正在阿默斯特学院进行两个实验。第一个项目是我们测试局部洛伦兹不变性(LLI)和CPT不变性的实验的继续。LLi是这样一个概念，即物理定律在所有局部惯性系中都是相同的，并且与它们在空间中的方位无关。CPT是离散对称性电荷共轭、宇称和时间的乘积。没有观察到违反LLI或CPT的情况。如果观测到违反，我们对基础物理的大部分理解将不得不从根本上改变。我们比较了汞和铯磁力计的相对进动频率作为外加磁场相对于“固定星”方向的函数。这种比较对LLI破坏首选宇宙框架与电子、中子和质子自旋之间的耦合很敏感。随着我们最近完成的实验，我们对几个违反LLI条款的行为设置了新的限制。有人指出，这些极限实际上可能会探测普朗克尺度上的物理学，弦理论认为可能会出现违规现象。我们决定用一种新设计的磁力计来代替，这种磁力计的灵敏度至少要高出二十倍。在这个水平上，实验将提供几种可能违反LLI和CPT的可能机制的最严格的重原子测试。在我们的第二个项目中，我们正在探索利用从基态的v=0，J=1到三重态B的v‘=0，J’=1的跃迁来激光冷却氟化铊(TLF)的可能性。使用激光冷却分子的方法直到最近才取得一定程度的成功。激光冷却分子的困难源于可用于衰变的无数种可能状态。很难找到一个循环过渡，它将允许实现显著冷却所需的数万个吸收/排放循环。在最近的工作中，我们已经证明，只需一台冷却激光器和一台再泵浦激光器，就可以在这种跃迁中实现数千个光子循环，而不会对其他能级造成重大损失。这应该允许低温光束的横向冷却和准直。在这里，我们打算对其他关键的弗兰克-康登因子进行精确测量。他们的决心将准确地告诉我们，需要多少次再泵浦激光才能使TLF的低温光束停止工作。我们还打算测量B态超精细结构(HFS)和同位素位移。HFS在决定到其他转动能级的损失率方面起着关键作用。如果TLF的激光冷却和俘获是可能的，这将为高精度地搜索Tl核的电偶极矩打开了可能性。这样的实验对Tl核的希夫矩很敏感，而它又对质子电火花和核相互作用中的时间反转破坏很敏感。这两个项目都把研究自然界的基本对称性作为他们的长期目标。尽管它们是相对温和的桌面实验，但它们可能会对粒子物理产生重要的影响。局域Lorentz不变性实验可以对弦理论提供限制，而未来的TLF电偶极矩实验将测试质子和核相互作用中的时间反转对称性。这些项目利用原子和激光物理的精密技术，为未来的科学家提供了广泛和灵活的培训。TLF实验将使我们的学生接触到分子激光冷却这一令人兴奋的新兴领域。这个项目很好地赞扬了大卫·霍尔教授在这里所做的BEC工作，以及我们的新助理教授大卫·汉纳克正在进行的UV激光开发，这是他捕获单离子工作的一部分。在过去的29年里，我们在阿默斯特的基本对称性实验吸引了许多有才华的本科生投身于物理学的职业生涯。该项目将延续我们追求最先进实验的传统，同时为本科生提供令人兴奋的研究机会和宝贵的培训。

We are pursuing two experiments at Amherst College. The first project is a continuation of our experiment to test Local Lorentz Invariance (LLI) and CPT invariance. LLI is the notion that the laws of physics are the same in all locally inertial frames and independent of their orientation in space. CPT is the product of the discrete symmetries charge conjugation, parity and time. No violation of either LLI or CPT has ever been observed. Much of our understanding of fundamental physics would have to be radically altered if a violation is observed. We compare the relative precession frequencies of Hg and Cs magnetometers as a function of the orientation of an applied magnetic field with respect to the "fixed stars". This comparison is sensitive to LLI violating couplings between a preferred universal frame and the electron, neutron and proton spins. With our recently completed experiment, we have placed new limits on several LLI violating terms. It has been pointed out that these limits may actually probe physics on the Planck scale, where String Theory suggests that violations might occur. We indend to replace the magnetometers with ones of a new design that should be at least a factor of twenty more sensitive. At this level, the experiment will provide the most stringent heavy-atom test of several possible mechanisms for violating LLI and CPT.In our second project we are exploring the possibility of laser cooling thallium fluoride (TlF) using a transition between the v=0, J=1 of the ground state to the v'=0,J'=1 state of the triplet B state. Methods to cool molecules using lasers have only recently achieved some level of success. The difficulty with laser-cooling of molecules stems from the myriad of possible states available for decay. It is hard to find a cycling transition which will allow the tens of thousands of absorption/emission cycles that are required to achieve significant cooling. In recent work, we have demonstrated that with only one cooling laser and one repump laser it should be possible to achieve several thousand photon cycles on this transition without significant loss to other levels. This should allow transverse cooling and collimation of a cryogenic beam. Here, we intend to make precision measurements of the other critical Franck-Condon factors. Their determination will tell us precisely how many repump lasers would be required to bring a cryogenic beam of the TlF to rest. We also intend to measure the B state hyperfine structure (HFS) and isotope shifts. The HFS plays a critical role in determining the rate of loss to other rotational levels. If the laser cooling and trapping of TlF is possibile, this would open up the possibility of performing a high-precision search for the electric dipole moment of the Tl nucleus. Such an experiment is sensitive to the Schiff moment of the Tl nucleus which is in turn sensitive to the proton edm and time-reversal violation in the nuclear interaction.Both of these projects have as their long-term goal the investigation of the fundamental symmetries of nature. Even though they are relatively modest table-top experiments, they have important possible implications for particle physics. The local Lorentz invariance experiment can provide limits on String Theory while a future thallium fluoride (TlF) electric-dipole moment experiment would test time-reversal symmetry in the proton and in the nuclear interaction. These projects, using the precision techniques of atomic and laser physics, provide a broad and flexible training for future scientists. The TlF experiment will expose our students to the exciting and emerging field of the laser-cooling of molecules. This project nicely compliments both the BEC work being done here by Prof. David Hall and the uv laser development that is being pursued by our new assistant Professor David Hanneke as part of his work on trapping single ions. Our fundamental symmetries experiments at Amherst have drawn many talented undergraduates into careers in physics over the last 29 years. This project will continue our tradition of pursuing state of the art experiments while providing exciting research opportunities and valuable training for undergraduates.