Precision Neutron Decay Measurements

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。中子是普通物质的基石之一。然而，当脱离稳定原子核的限制时，中子是不稳定的，衰变成质子、电子和平均寿命约为15分钟的反中微子。这种衰变是由弱核力支配的，核力是自然界的四种基本力量之一。通过仔细测量发射粒子的能量和方向以及原始中子的自旋轴，可以揭示弱力基本性质的微妙细节。我们让冷中子束(移动速度小于2000米/S)通过各种仪器，用来精确测量中子衰变寿命和角关联。我们使用这些结果来测试粒子相互作用的标准模型，并寻找新物理的证据。中子寿命被用来从大爆炸模型计算早期宇宙中产生的轻元素的丰度。一些研究生和本科生以及博士后研究人员参与了这项研究计划。除了学习中子衰变科学外，他们还接受了中子源研究的物理学和方法论方面的广泛教育，这为他们在学术界和工业界从事与中子科学有关的广泛职业做好了准备。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The neutron is one of the building blocks of ordinary matter. However, when free from the confines of a stable atomic nucleus, the neutron is unstable and decays into a proton, electron, and antineutrino with an average lifetime of about 15 minutes. This decay is governed by the weak nuclear force, one of the four basic forces of nature. By carefully measuring the energies and directions of the emitted particles and the spin axis of the original neutron, subtle details of the fundamental nature of the weak force can be revealed. We pass beams of cold neutrons (moving less than 2000 m/s) through a variety of apparatus designed to make precise measurements of the neutron decay lifetime and angular correlations. We use these results to test the Standard Model of particle interactions and look for evidence of new physics. The neutron lifetime is used to calculated the abundances of light elements produced in the early universe from the big bang model.A number of graduate and undergraduate students, as well as postdoctoral researchers, participate in this research program. In addition to learning the science of neutron decay, they are educated broadly in the physics and methodology of research at neutron sources, which prepares them for a wide range of careers related to neutron science in academia and industry.