Fundamental symmetry tests with optically trapped radioactive neutral atoms

我们使用激光捕获和冷却技术来捕获放射性原子，并精确测试弱相互作用的标准模型。被限制在1毫米大小的云中，原子核经历β衰变，产生三种产物：正电子、中微子和子核。女儿移动缓慢，会在一纳米的材料中停下来，但它可以自由地逃离陷阱。通过检测它与正电子的重合，我们可以比以前的实验更直接地测量动量，从而测量中微子的角分布。已知的电弱相互作用是由自旋为1的矢量玻色子、W+、W-和Z0介导的。这些只产生左手中微子：奇偶性（镜像对称）被极大地破坏了。我们测试这些模型特征。我们现在通过测量自旋为0的原子核的纯费米衰变中的β -中微子相关，发表了第一代粒子与标量相互作用耦合的最佳限制。我们建议将这些测量方法提高三倍。我们发表了一篇关于重中微子与电子中微子混合的缺失质量的研究，直接限制了天体物理学对混合物的兴趣水平。我们正在学习其他原子核的自旋极化，并通过独立于衰变的原子方法测量它们的极化。当与β -后坐力巧合相结合时，我们可以测量出新的相关性。我们已经测量了37K的中微子不对称性，精度为3%，我们打算将其提高到0.1%。子核方向的自旋不对称性在纯伽莫夫-泰勒衰变中消失。我们现在可以独特地测量这种与原子阱的关系，由于它消失了，许多极化系统变得不重要了。我们的目标是达到0.1%的精度，以测试辐射介子衰变中PIBETA合作报告的非零张量相互作用的提示。这是两位硕士生的课题。我们的第二个博士学位很快就要毕业了，接着是第三个博士学位，在一种新型陷阱上获得了硕士学位，平均一次只毕业一个本科生。

We use laser trapping and cooling techniques to capture radioactive atoms and precisely test the Standard Model of the weak interaction. Confined in a 1 mm-sized cloud, the nuclei undergo beta decay, producing three products: a positron, a neutrino, and a daughter nucleus. The daughter moves slowly and would stop in a nm of material, but it freely escapes the trap. By detecting it in coincidence with the positron, we can measure the momentum and hence the angular distribution of neutrinos more directly than in previous experiments.   The known electroweak interaction is mediated by spin-1 vector bosons, the W+, W-, and Z0. These only produce left-handed neutrinos: parity (mirror symmetry) is maximally violated. We test these model features.   We have now published the best limits on scalar interactions coupling to the first generation of particles by measuring the beta-neutrino correlation in the pure Fermi decay of a spin-0 nucleus. We propose to improve these measurements by a factor of three. We published a missing-mass search for heavy neutrinos mixing with the electron neutrino, directly constraining admixture levels of interest to astrophysics.   We are learning to spin-polarize other nuclei and measure their polarization by atomic methods independent of their decays. When combined with beta-recoil coincidences, we can measure novel correlations. We have measured the neutrino asymmetry of 37K to 3% accuracy, which we intend to improve to 0.1%   The spin asymmetry of the direction of the daughter nuclei vanishes in pure Gamow-Teller decay. We can now uniquely measure this correlation with the atom trap, and since it vanishes many polarization systematics become unimportant. Our goal is to reach 0.1% accuracy to test hints of a nonzero tensor interaction reported by the PIBETA collaboration in radiative pion decays. This is the project of two M.Sc. students. We will soon graduate our 2nd Ph.D., to be followed by a 3rd, graduated an M.Sc. on a new type of trap, and average one undergrad at a time.