Acquisition of a Spectrometer and Detectors for Precision Nuclear Physics Measurements of Neutron Beta Decay

超导螺线管光谱仪和最先进的低能电子探测器将首次使用超冷中子（UCN）对中子衰变进行一系列高精度测量。特别是中子自旋方向与电子动量之间的角相关性(A)将以0.2%的统计精度和实质上更小的系统误差进行测量。这表明，在一个系统不确定度明显不同且小得多的实验中，与目前的最佳测量结果相比，改进了近五倍。中子β衰变中a相关性的高精度测量可以与中子和介子寿命的测量相结合，以提取u-夸克/d-夸克弱混合，也称为V_ud，这是Cabibbo-Kobayashi-Maskawa （CKM）矩阵的关键组成部分。V_ud的改进测量可以通过测试该矩阵的统一性来提供超越标准模型的物理。

A superconducting solenoidal spectrometer and state-of-the-art detectors for low energy electrons will be used for a series of high precisionmeasurements of neutron beta-decay using, for the first time, Ultra-Cold Neutrons (UCN). In particular the angular correlation (A) between the neutron spin direction and the electron momentum will be measured with a statistical precision of 0.2% and substantially smaller systematic errors. This represents nearly a factor of five improvement over the present best measurements in an experiment with significantly different and considerably smaller systematic uncertainties. High-precision measurements of the A-correlation in neutron beta-decay can be combined with measurements of the neutron and muon lifetimes toextract the u-quark/d-quark weak mixing also known as V_ud - a key component of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. Improvedmeasurements of V_ud can provide access to physics beyond the Standard Model by testing the unitarity of this matrix.