Nucleon Structure Through Electron and Photon Scattering

这项研究的目的是通过实验来突破现有知识的极限，检验关于强作用力的公认理论的有效性。虽然这些理论被认为是正确的物质基础理论，但本提案中描述的精确实验旨在限制理论预测。特别是，所谓的标准模型提供了电磁和自然“弱”力的统一，并且设计了一个实验来测量质子的弱电荷，精度为百分之几。这个被称为Q-weak的实验将在杰弗逊实验室进行，并将清楚地确定对标准模型的任何必要修正（或确切地证实它）。在杰弗逊实验室的另一个实验中，我们正在研究一种新的粒子（有时被称为“外来”重子）共振，这种共振是由群论和强相互作用的全局对称性所预测的。如果这种粒子存在，那么它将是同类粒子中的第一个，被称为五夸克，它代表了已知的3夸克物体（如质子）和夸克-反夸克粒子之间的结合。在布鲁克海文国家实验室的激光电子伽马源（LEGS）设施中正在进行其他实验。这些实验也被设计用来测试众所周知的物理学原理（规范理论），这些原理将质子的“自旋”与光子束撞击质子或中子所产生的所有散射粒子的测量联系起来。这个实验需要开发一种新型的固体氘化氢靶，它可以被高度极化。目的是了解更多关于是什么导致了质子或中子的“自旋”结构。

The goal of this research is to test the validity of accepted theories of the strong force, using experiments that push the limits of current knowledge. While the theories are believed to be the correct underlying theory of matter, precision experiments described in this proposal are designed to constrain the theoretical predictions. In particular, the so-called Standard Model provides the unification of electromagnetic and "weak" forces of nature, and one experiment is designed to measure the weak charge of the proton at a precision of a few percent. This experiment, called Q-weak, will be performed at Jefferson Lab and will clearly identify any necessary corrections to the Standard Model (or solidly confim it). In another experiment, also at Jefferson Lab, we are investigating a new kind of particle (sometimes called an "exotic" baryon) resonance that was predicted by group theory and global symmetries of the strong interaction. If this particle exists, then it is the first of its kind, called the pentaquark, and represents a marriage between the known 3-quark objects (like the proton) and quark-antiquark particles.Additional experiments are being carried out at the laser electron gamma source (LEGS) facility at Brookhaven National Lab. These experiments are also designed to test well-known principles of physics (gauge theories) that connects the "spin" of the proton to measurements of all scattered particles made from a photon beam hitting a proton or a neutron. This experiment requires the development of a novel solid HD (hydrogen deuteride) target that can be polarized to a high degree. The goal is to learn more about what causes the "spin" structure of the proton or neutron.