Charge Structure of the Neutron

这项研究解决了一个关于中子（物质的基本组成部分之一）电荷结构性质的基本问题：中子中净零电荷的组成夸克的空间分布是什么？这个问题在杰弗逊实验室实验93-038中通过准弹性地散射来自中子氘的纵向极化电子来解决。氘由一个松散结合在一起的中子和一个质子组成；它代表了最好的中子靶。在与中子碰撞时，电子将极化传递给中子。中子偏振矢量的两个分量都位于散射平面内：横向（或横向）分量与中子动量正方向，纵向分量与中子动量平行（或反平行）。通过测量两侧和纵向极化，可以提取一个称为中子电形状因子的量，它由字母GEN指定。GEN作为动量传递的函数的测量与中子内电荷的空间分布有关。我们对中子内部电荷密度的认识的不确定性随着对GEN的测量扩展到更高的动量转移而变得更小。GEN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、对电结构函数进行详细的微观计算以及解释违反宇称实验结果所需的基本量。目前的研究包括执行和完成对从93-038获得的数据的详细分析，准备发表结果，准备和执行一个新的实验，以更高的动量转移提取GEN。

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.