TRIUMF Neutral Atom Trap for beta decay angular correlations: searches for new interactions

核β衰变相关实验帮助建立了弱相互作用的本质，这是一种只与左手轻子(即电子和中微子)耦合的自旋1玻色子(像光子，但质量很大)的理论。出射粒子的角分布，如果测量到千分之几，对新的相互作用很敏感，这些相互作用可能会产生不同利手的轻子。*我们测量了37K衰变中相对于核自旋的β不对称性为Aβ=-0.5706+-0.0018。这是吴中山最初的宇称破坏观测，我们的β不对称测量在任何原子核或中子中都具有最好的分数精度(即最小不确定度/Aβ)，并与理论一致。我们的Abeta平均值可以限制产生错误的中微子的相互作用，或者结合其他实验，测试具有有限自旋和磁矩的原子核是否都具有相同的β衰变本征强度。我们将通过在37K下更好地测量Abeta和其他可观测数据来进一步探索这种可能的“守恒矢量流”破坏。*Abeta对Beta能量的依赖仍在一名博士生的分析中，并且对新的4费米子有效场论相互作用单独敏感。我们建议的测量，包括子核方向相对于初始核自旋的不对称，探测产生错误正电子的新相互作用：这些可观测到的尺度具有螺旋度因子(电子质量)/(电子能量)，在较高能量时通常被抑制，使我们的测量成为补充。我们测量的关键是我们证明了用我们的原子陷阱技术高度极化原子核的能力，我们还计划利用辐射β衰变产物的三个独立动量进行时间反转对称性测试，这是在相对较低能量尺度下的第一代粒子中唯一的一种测试。我们正在重建从92Rb 0-到0+衰变的中微子能谱，从其他产品的动量，只使用β方向，而不是它的能量。几次从0到0+的衰变共同产生了反应堆中约30%的高能中微子，虽然原则上该理论是根据两个与核结构有关的矩阵元素来合理定义的，但在这种衰变类型的β能谱测量方面，文献中存在着不一致的地方。同时测量贝塔-中微子关联将帮助我们提取两个矩阵元素，以更好地测试第一禁止理论。*我们预计继续为两名研究生维持TRIUMF EEC高优先级实验，因此要求额外资金开始第三名学生，同时第二名学生完成博士学位的分析部分。

Nuclear beta decay correlation experiments helped establish the nature of the weak interaction, a theory with spin-1 bosons (like the photon, but massive) coupling only to left-handed leptons (i.e. electrons and neutrinos). The angular distribution of the outgoing particles, if measured to part per thousand, is sensitive to new interactions that can produce leptons with different handedness. ******We have measured the beta asymmetry with respect to the nuclear spin in 37K decay to be Abeta=-0.5706+-0.0018. This was C.S. Wu's original parity-violating observable, and our beta asymmetry measurement has the best fractional accuracy (i.e. smallest uncertainty/Abeta) in any nucleus or the neutron, and is in agreement with theory. Our average value of Abeta can either constrain interactions producing wrong-handed neutrinos, or, combined with other experiments, tests whether nuclei with finite spin and magnetic moment all have the same intrinsic strength of beta decay. We will further explore this possible "conserved vector current" violation by measuring Abeta and other observables better in 37K.******The dependence of Abeta on beta energy is still under analysis by a Ph.D. student, and is separately sensitive to new 4-fermion effective field theory interactions. Our proposed measurements, including the asymmetry of the direction of progeny nuclei with respect to the intial nuclear spin, probe new interactions producing wrong-handed positrons: these observables scale with a helicity factor (electron mass)/(electron energy) that is typically suppressed at higher energy, making our measurements complementary.******Key to our measurements is our demonstrated ability to highly polarize the nuclei with our atom trap techniques, and to determine the polarization of the nuclei decaying to 0.1% accuracy by atomic methods in situ.******We also plan a time reversal symmetry test using the three independent momenta of the products of radiative beta decay, a unique test in the first generation of particles at relatively low energy scale.******Reactor neutrinos show anomalies in their total number and energy dependence. We are reconstructing the neutrino energy spectrum from 92Rb 0- to 0+ decay from the momenta of the other products, using only the beta direction and not its energy. Several 0- to 0+ decays together produce about 30% of the higher-energy neutrinos from a reactor, and while in principle the theory is reasonably defined in terms of two nuclear structure-dependent matrix elements, there is inconsistency in the literature between difficult beta energy spectrum measurements in this type of decay. Simultaneous measurement of the beta-neutrino correlation will help us extract the two matrix elements to better test the 1st-forbidden theory.******We expect to continue to maintain TRIUMF EEC high priority experiments for 2 graduate students at a time, so ask for additional funds to start a 3rd student while the 2nd student completes the analysis part of a Ph.D.