Selected Problems in Medium Energy Physics

0072466 Danagoulian本提案请求为杰斐逊实验室的两个实验项目的开发和解释提供支持：中性介子寿命的精确测量，实验“PrimeX”和测量中子的电磁形状因数，实验“GEN”。PrimeX实验将对中性pi介子的寿命进行高精度测量。对介子衰变过程的理论描述导致了QCD中最准确的预测之一，即描述夸克之间强相互作用性质的量子场论。本实验测量寿命的精度为~1.4%，与理论不确定度一致。它是核物理的基础实验之一。中子是一种电中性粒子。然而，它拥有一种电磁结构。“Gen”实验通过精确测量中子的电磁形状因数Gen和GmN，解决了中子电磁结构的基本问题。在核结构和QCD的基准计算中，需要了解中子的内部结构。尽管Gen很重要，但它仍然鲜为人知，对实验者来说是一个巨大的挑战。除了其科学重要性外，拟议的研究计划还将为我们的学生提供独特的实验核物理研究机会，因此将对他们的培训和教育产生非常强烈的影响。

0072466Danagoulian This proposal requests support for development and interpretation of two experimental programs at Jefferson Lab: neutral pi-meson lifetime precise measurement, experiment "PrimEx" and measurement of the electric and magnetic form factors of the neutron, experiments "Gen". The experiment "PrimEx" will perform a high precision measurement of the lifetime of the neutral pi-meson. The theoretical description of the process of meson decay results in one of the most accurate predictions in QCD, the quantum field theory that describes the properties of the strong interaction between quarks. The present experiment will measure the lifetime with an accuracy of ~1.4% which is consistent with the theoretical uncertainties. It is one of the fundamental experiments in nuclear physics. The neutron is an electrically neutral particle. Nevertheless it possesses an electromagnetic structure. The "Gen" experiments address the fundamental issue of the electromagnetic structure of the neutron by performing precise measurements of the neutron electric and magnetic form factors, Gen and Gmn. The knowledge of the internal structure of the neutron is needed for benchmark calculations in nuclear structure and QCD. Despite its fundamental importance, Gen is still poorly known, and stands as a significant challenge for the experimentalists. Besides its scientific importance the proposed research program will provide our students with unique research opportunities in experimental nuclear physics, and therefore will have a very strong impact on their training and education.