Research in Intermediate Energy Physics

将研究在中能核物理和粒子物理学中基本感兴趣的新问题。该计划最初的重点将是精确测量带电介子的衰减率，准确度约为0.5%。这一过程为研究弱u-d夸克混合提供了理论上最明确的手段，它直接测试了夸克-轻子的普适性，因此可以约束某些方面的物理学，超越目前的标准模型。拟议中的实验是分阶段努力的第一步，目的是提高目前4%的介子β衰减率的精度，接近并最终超过纯费米核β衰变的精度(现在约为0.2%)。在第一步提出的精度水平下，我们的测量将在介子中提供对CVC假说最敏感的测试。大立体角探测器将探测静止的衰变，也将对其他稀有的介子衰变敏感。PSI已经批准了1989年的初步运行，弗吉尼亚大学的探测器开发工作目前正在进行中。其他实验承诺包括精确测量PSI静止的介子衰变中的介子动量，测量CERN标度区中子和质子的自旋相关结构函数，以及与CEBAF未来实验相关的工作。

New problems of basic interest in nuclear and particle physics at intermediate energies will be studied. The initial emphasis in the program will be on a precise measurement, with ~0.5 percent accuracy, of the rate of decay of charged pions. This process provides the theoretically most unambiguous means to study weak u-d quark mixing which directly tests quark- lepton universality and can thus constrain certain aspects of physics beyond the present Standard Model. The proposed experiment represents a first step in a staged effort at improving the present 4 percent accuracy of the pion beta decay rate, to approach and eventually surpass that of pure Fermi nuclear beta decays (now ~0.2 percent). At the level of accuracy proposed for the first step, our measurement will provide the most sensitive test of the CVC hypothesis in a meson. A large-solid-angle detector will detect decays at rest and will also be sensitive to other rare pion decays. Initial runs have been approved for 1989 at PSI, and detector development work is presently under way at University of Virginia. Other experimental commitments include a precise measurement of the muon momentum in pion decay at rest at PSI, a measurement of the spin-dependent structure functions of the neutron and proton in the scaling region at CERN, and work related to future experiments at CEBAF.