Charge Structure of the Neutron

这项研究解决了一个关于中子电荷结构性质的基本问题-物质的基本构件之一：在净电荷为零的中子中，组成夸克的空间分布是什么？这个问题在杰斐逊实验室第93-038号实验中通过从中子铟准弹性地散射纵向极化的电子来解决。氢由一个中子和一个质子松散地结合在一起；它代表了现有的最好的中子靶。在与中子的碰撞中，电子将极化转移到中子。中子极化矢量的两个分量都位于散射面：横向(或侧面)分量与中子动量垂直，纵向分量与中子动量平行(或反平行)。通过测量横向极化和纵向极化，可以提取一个称为中子电形状因数的量，它由字母Gen表示。作为动量转移函数的Gen的测量与中子内部电荷的空间分布有关。随着Gen的测量扩展到更高的动量转移，我们对中子内部电荷密度的知识的不确定性变得更小。关于基因的知识对于理解物质的结构是必不可少的。Gen是挑战核子结构模型、对电子结构函数进行详细的微观计算以及解释宇称破坏实验结果所需的基本量。目前的研究包括对从E93-038获得的数据进行和完成详细的分析，准备发表结果，以及准备和进行一项新的实验，以在更高的动量传输下提取基因。

This research addresses a fundamental question regarding the nature ofthe charge structure of the neutron --- one of the basic building blocksof matter: What is the spatial distribution of the constituent quarkswithin the neutron, which has a net zero charge? This question wasaddressed in Jefferson Laboratory Experiment 93-038 by scatteringlongitudinally polarized electrons quasielastically from a neutron indeuterium. Deuterium consists of a neutron and a proton bound looselytogether; it represents the best neutron target available. In acollision with the neutron, the electron transfers polarization to theneutron. Both components of the neutron polarization vector lie in thescattering plane: The transverse (or sideways) component is normal tothe momentum of the neutron, and the longitudinal component is parallel(or antiparallel) to the neutron momentum. By measuring both thesideways and the longitudinal polarizations, it is possible to extract aquantity called the neutron electric form factor, which is designated bythe letters GEN. Measurements of GEN as a function of momentum transferare related to the spatial distribution of charge within the neutron.The uncertainty in our knowledge of the interior charge density of theneutron becomes smaller as measurements of GEN are extended to highermomentum transfer. Knowledge of GEN is essential to understanding thestructure of matter. GEN is a fundamental quantity needed to challengemodels of nucleon structure, to make detailed microscopic calculationsof electric structure functions, and to interpret the results ofparity-violating experiments. The current research involves carryingout and completing a detailed analysis of the data obtained fromE93-038, preparing the results for publication, and preparing andcarrying out a new experiment to extract GEN at still higher momentumtransfers.