RUI: The aCORN Experiment to Measure the Beta-Neutrino Asymmetry in Neutron Decay

aCORN合作计划测量中子衰变中的β -中微子不对称性，“a”，相对不确定度为1%。自由中子的衰变提供了一个近乎理想的系统，在这个系统中我们可以探测到电弱相互作用标准模型的极限，因为在标准模型中可以精确地计算衰变系数。目前对标准模型自洽性的一些测试受到“a”中4%的实验不确定性的限制。aCORN实验依赖于将中子衰变分为两类；一种是和中子几乎平行发射，另一种是它们几乎反平行发射。一组电场和磁场将粒子引导到3米长的真空容器两端的探测器上。有了这个仪器，“a”的测定就简化为计算这两类质子的数目。该装置的设计目的是将系统误差降低到0.5%以下。该实验将于2012年春季在NIST的中子指南NG-6上开始其第一次物理运行，并将在2013年投入使用时转移到新的指南NG-C上。在整个操作阶段，汉密尔顿学院将参与实验的几个方面。我们将管理分布式数据分析工作，包括NIST的前端数据缩减软件和整个合作过程中分布的最终分析软件。我们将继续对磁场和电场几何形状进行建模，作为蒙特卡罗模拟的输入，并作为改进物理设备的一种方式。在运行结束时，我们将使用来自热灯丝的电子进行校准检查。我们还将继续维护磁场对准设备，包括电源和一个磁场测绘机器人。让本科生参与研究是汉密尔顿学院文化的重要组成部分。我们认为研究对于吸引优秀的学生进入科学领域，培养具有科学知识的毕业生，并激励他们在毕业后继续从事科学研究至关重要。我们有让本科生参与研究的历史，大约一半的研究学生继续接受物理或工程方面的进一步教育。此外，汉密尔顿大学的培养环境对于吸引女性学习物理学尤为重要。通过我们小组的学生中有四分之一是女性，这八名女性中有六名读了科学或教育专业的研究生。拟议的工作将继续涉及大量的本科生，无论是在汉密尔顿还是在NIST。我们的学生可以在Hamilton老师的密切指导下拥有一个可管理的项目，然后将他们的作品整合到国家实验室环境中的最终系统中。

The aCORN collaboration intends to measure the beta-neutrino asymmetry, 'a,' in neutron decay with a relative uncertainty of 1%. The decay of the free neutron provides a nearly ideal system where we could probe the limits of the Standard Model of the electro-weak interaction because the decay coefficients can be accurately calculated in the standard model. Some current tests of the self-consistency of the Standard Model are limited by the 4% experimental uncertainty in 'a.' The aCORN experiment relies on separating neutron decays into two classes; one in which the beta and neutron are emitted nearly parallel, and one in which they are nearly anti-parallel. A set of electric and magnetic fields guide the particles to detectors at opposite ends of a 3m long vacuum vessel. With this apparatus, the determination of 'a' is reduced to counting the numbers of protons in the two classes. The apparatus has been designed to reduce systematic errors below 0.5%. The experiment will begin its first physics run on neutron guide NG-6 at NIST in the spring of 2012, and will move to the new guide NG-C when it becomes available in 2013. Hamilton College will be involved in several aspects of the experiment throughout the operations phase. We will manage the distributed data analysis effort including both front end data reduction software at NIST and final analysis software distributed throughout the collaboration. We will continue to model magnetic and electric field geometries as inputs to a Monte Carlo simulation and as a way to improve the physical apparatus. Toward the end of the run we will implement an alignment check using electrons from a hot filament. We will also continue to maintain magnetic field alignment equipment including power supplies and a field mapping robot.Including undergraduates in research is a vital part of the culture at Hamilton College. We see research as crucial to attracting strong students to the sciences, producing scientifically knowledgeable graduates, and inspiring them to continue in science after they graduate. We have a history of including undergraduates in research, and about half of our research students go on to further education in physics or engineering. Furthermore, the nurturing environment at Hamilton is especially important for attracting women to physics. A quarter of the students that have come through our group are women, and six of these eight women have gone to graduate school in science or education. The proposed work will continue to involve significant numbers of undergraduates, both at Hamilton and at NIST. Our students can own a manageable piece of the project under close faculty mentoring Hamilton, and later integrate their piece into the final system in the environment of a national lab.