Parity Nonconserving Spin Rotations Of The Neutron

现代物理学的一个目标是理解和描述自然界中起作用的力。这一计划缺少的一项内容是确定原子核中中子和质子之间的弱相互作用强度。弱相互作用的特征是破坏了宇称(左-右)对称性。我们计划从美国国家标准与技术研究所的反应堆发射一束极化的中子束，穿过一个一米长的液氦靶子。束流中的中子和氦原子核(阿尔法粒子)之间的微弱作用力将导致束流极化绕束流方向以右旋或左旋方向旋转约百万分之一度。我们建议测量这一微小的“中子自旋的宇称非守恒转动”，以提取中子和氦原子核之间的弱力的符号和强度。我们的结果将与类似的质子束实验结果相比较，以提供对弱核力的更完整的表征。***

***9804038HeckelA goal of modern physics is to understand and characterize the forces that are at work in nature. A missing element of this program is the determination of the weak interaction strength between the neutrons and protons in an atomic nucleus. The signature of the weak interaction is the violation of parity (left-right) symmetry. We propose to send a beam of polarized neutrons from the National Institute of Standards and Technology reactor through a one meter long target of liquid helium. The weak force between the neutrons in the beam and the helium nuclei (alpha particles) will cause the beam polarization to rotate about the beam direction in a right or left handed screw sense, by approximately one millionth of a degree. We propose to measure this minute "parity nonconserving rotation of the neutron spin" to extract the sign and strength of the weak force between neutrons and helium nuclei. Our result will be compared to the results from similar experiments with proton beams to provide a more complete characterization of the weak nuclear force. ***