Swanson H E, Heckel B R, Bass C D, Bass T D, Dawkins J M, Horton J C, Luo D, Snow W M, Walbridge S B, Crawford B E, Gan K, Micherdzinska A M, Huffer C, Markoff D M, Mumm H P, Nico J S, Sarsour M, Sharapov E I, Zhumabekova V
University of Washington and Center for Experimental Nuclear Physics and Astrophysics, Box 354290, Seattle, Washington 98195, USA.
LeMoyne College, 1419 Salt Springs Road, Syracuse, New York 13214, USA.
Phys Rev C. 2019;100(1). doi: 10.1103/PhysRevC.100.015204.
Neutron spin rotation is expected from quark-quark weak interactions in the standard model, which induce weak interactions among nucleons that violate parity. We present the results from an experiment searching for the effect of parity violation via the spin rotation of polarized neutrons in a liquid He medium. The value for the neutron spin rotation angle per unit length in He, rad/m, is consistent with zero. The result agrees with the best current theoretical estimates of the size of nucleon-nucleon weak amplitudes from other experiments and with the expectations from recent theoretical approaches to weak nucleon-nucleon interactions. In this paper we review the theoretical status of parity violation in the He system and discuss details of the data analysis leading to the quoted result. Analysis tools are presented that quantify systematic uncertainties in this measurement and that are expected to be essential for future measurements.
在标准模型中，夸克 - 夸克弱相互作用预计会导致中子自旋旋转，这种相互作用会引发核子间违反宇称的弱相互作用。我们展示了一项实验的结果，该实验通过在液氦介质中极化中子的自旋旋转来寻找宇称违反效应。氦中单位长度的中子自旋旋转角的值，以弧度/米为单位，与零一致。该结果与其他实验对核子 - 核子弱振幅大小的当前最佳理论估计以及近期弱核子 - 核子相互作用理论方法的预期相符。在本文中，我们回顾了氦系统中宇称违反的理论现状，并讨论了得出上述结果的数据分析细节。还介绍了分析工具，这些工具量化了该测量中的系统不确定性，并且预计对未来的测量至关重要。
