Parity Violating Electron Scattering at Jefferson Lab

在夸克水平上理解核子的结构在粒子和核物理学中是非常重要的。 一个被认为对夸克自由度直接敏感的观测结果是极化方向平行和反平行于入射电子动量的电子与非极化质子弹性散射截面的差异。 这种违反宇称的不对称性是由入射电子交换光子和交换中性弱玻色子的过程之间的干涉造成的。 特别是宇称破缺的弹性电子质子散射可以确定核子的奇异电荷和磁形状因子，它们描述了奇异夸克对核子的贡献，沿着它们的动量转移，如果宇称破缺的电子核子散射实验可以从弹性通道扩展到特定的非弹性通道，可以清楚地获得关于核子内部夸克流的额外信息。 核子第一激发态δ共振的理解一直被认为是检验核子结构模型的重要手段。 在这种共振的电产生中，宇称违反不对称性可以隔离夸克流的等矢量贡献。 在电子散射中，通过中性弱玻色子的交换也能产生δ共振。 因此，弱过渡形状因子也有助于N-到-Delta过渡。路易斯安那理工学院应用物理研究中心（CAPS）的研究工作包括研究弹性和非弹性反应中的宇称违反电子散射。 CAPS在杰斐逊实验室（E00-006）的G 0实验中有重要的参与，该实验将研究弹性通道，并且是实验E97-104的发言人，“测量N到Delta转变中违反不对称性的奇偶性”。''

0072283Johnston Understanding the structure of the nucleon at the quark level is offundamental importance in particle and nuclear physics. An observableidentified as being directly sensitive to quark degrees of freedom isthe cross section difference between the elastic scattering of electronswith polarizations parallel and antiparallel to the incident electronmomentum from unpolarized protons. This parity violating asymmetryresults from the interference between the process in which an incidentelectron exchanges a photon and the one in which it exchanges a neutralweak boson. Specifically, parity violating elastic electron protonscattering allows determination of the nucleon strange charge andmagnetic form factors, which describe the contributions from strangequarks to the nucleon, along with their momentum transfer dependence.If parity violating electron nucleon scattering experiments are extendedbeyond the elastic channel into particular inelastic channels,additional information about the quark currents inside the nucleon canclearly be obtained. Understanding the Delta resonance, the firstexcited nucleon state, has always been considered an important test ofnucleon structure models. The parity violating asymmetry inelectroproduction of this resonance can isolate the isovectorcontributions to the quark currents. The Delta resonance can also beproduced in electron scattering via the exchange of the neutral weakboson. Thus, weak transition form factors also contribute to theN-to-Delta transition. Included in the research efforts of the Louisiana Tech Center forApplied Physics Studies (CAPS) is the study of parity violating electronscattering in both elastic and inelastic reactions. CAPS hassignificant involvement in the G0 experiment at Jefferson Lab (E00-006),which will investigate the elastic channel, and are spokespersons forexperiment E97-104, ``Measurement of the Parity Violating Asymmetry inthe N-to-Delta transition.''