Helium 3 ion chambers for precision neutron capture asymmetry measurements

我们目前对亚原子粒子的相互作用和性质的理解是由所谓的标准模型描述的。该模型目前将电磁相互作用、弱相互作用和强相互作用结合到一个框架中，并且在过去50年中在预测实验结果方面取得了广泛的成功。弱相互作用驱动中子衰变为质子，是星星产生能量的核心。强相互作用作用发生在称为夸克的亚原子粒子之间，并将中子和质子（核子）结合成核。尽管标准模型取得了成功，但很明显，它只是对驱动亚原子水平相互作用的过程的近似描述。支持这一论断的原因有很多，其中之一是这个模型有许多参数是以特别的方式进入理论的，以及它所描述的相互作用中明显遗漏了引力。因此，对标准模型各个方面的验证和对标准模型之外的新物理的探索是目前亚原子粒子物理研究的前沿。位于马尼托巴和温尼伯大学的一个小组发起了一个加拿大基础中子物理实验计划，以研究标准模型的预测。这里提出的工作涉及使用亚原子粒子之间的弱相互作用作为其基本性质的探针的研究。这些实验使用高强度中子源来寻找抛射体和给定目标之间反应中非常小的不对称性。对这些不对称性的测量是对核子内部非常小的影响的高灵敏度探针。该提案要求为建造氦3离子室提供资金，该室将用于中子捕获和衰变过程的精确测量。由于核子间的弱相互作用是在标准模型中预测的，但强相互作用以未知的方式进行了修改，因此建议的中子俘获过程中不对称性的测量本身就是标准模型的测试。

Our current understanding of the interactions and properties of subatomic particles is described by the so called Standard Model. The model currently combines the electromagnetic interactions, the weak interaction, and the strong interactions into one framework and has enjoyed extensive success in predicting experimental results over the past 50 years. The weak interaction drives the decay of neutrons into protons and lies at the heart of energy generation in a star. The strong interaction acts between subatomic particles called quarks and binds neutrons and protons (nucleons) into nuclei. Despite its success, it is apparent that the Standard Model is only an approximate description of the processes that drive interactions at the subatomic level. Among many reasons supporting this assertion are the fact that the model has many parameters which enter the theory in an ad hoc manner, as well as the glaring omission of gravity from the interactions it describes. The verification of all aspects of the Standard Model and the search for new physics beyond the Standard Model are therefore currently at the leading edge of subatomic particle physics research. A group based at the universities of Manitoba and Winnipeg has initiated a Canadian program in fundamental neutron physics experiments to investigate Standard Model predictions. The work proposed here involves studies which use the weak interaction between subatomic particles as a probe for their fundamental properties. The experiments use high intensity neutron sources to search for very small asymmetries in the reaction between the projectile and a given target. Measurements of these asymmetries are highly sensitive probes of very small effects inside nucleons. This proposal requests funding for the construction of helium 3 ion chambers which will be used for precise measurements in neutron capture and decay processes. Since the weak interaction between nucleons is predicted within the Standard Model, but modified in an unknown way by the strong Interaction, the proposed measurements of asymmetries in the neutron capture processes are Standard Model tests in their own right.