Research in Intermediate Energy Physics

中能物理研究

• 批准号: 0653356
• 负责人: Dinko Pocanic
• 金额: $ 82.2万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-05-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0653356&HistoricalAwards=false
• 关键词: Research; Intermediate; Energy; Physics

This project addresses certain basic aspects of the electroweak and strong interactions reflected in the properties of mesons and nucleons (particles found inside atomic nuclei) and their interactions at low energies. The strong and weak interactions are responsible for the structure of matter at the smallest known scale, a femtometer (size of the hydrogen nucleus) or less. The research is motivated by the fact that the present comprehensive theory -- the Standard Model (SM) -- is known to be incomplete. The rare decay of the pi-meson (pion) into an electron and a neutrino, occurring once in about ten thousand ordinary pion decays, provides a theoretically extraordinarily clean window to certain possible extensions of the SM, at a very large mass scale not directly accessible at any existing or planned accelerators. The PEN experiment, mounted at the Paul Scherrer Institute, Switzerland, by an international collaboration of seven institutions led by the University of Virginia (UVa) group, builds on the success of the PIBETA experiment which improved by about an order of magnitude the accuracy of several rare decay modes of the pion and muon (a massive relative of the electron) in a series of measurements from 1999 through 2004. A new project, encompassing experiments "Nab" and "abBA," has been initiated at the Spallation Neutron Source at Oak Ridge National Lab in Tennessee, with the aim to measure precisely and simultaneously several of the decay parameter of the neutron beta decay. Through their precision, these experiments will explore similarly interesting possible extensions to the SM. During the past five years this program has resulted in four doctoral degrees at UVa. Two UVa Ph.D. students are currently working towards their theses, plans call for a third to join the group soon. Each year typically one to two undergraduate students are engaged in research on this project, thus gaining practical laboratory experience.

该项目涉及反映在介子和核子（原子核内发现的粒子）的性质及其在低能量下的相互作用中的电弱和强相互作用的某些基本方面。 强相互作用和弱相互作用决定了已知最小尺度下的物质结构，即一毫微微米（氢核大小）或更小。这项研究的动机是，目前的综合理论--标准模型（SM）--已知是不完整的。 π介子（π介子）衰变为电子和中微子的几率很小，普通π介子的衰变大约每一万次才发生一次，这在理论上为SM的某些可能扩展提供了一个非常干净的窗口，在任何现有或计划中的加速器都无法直接访问的非常大的质量尺度上。 PEN实验由弗吉尼亚大学（UVa）小组领导的七个机构的国际合作在瑞士保罗谢勒研究所进行，建立在PIBETA实验的成功基础上，该实验在1999年至2004年的一系列测量中将π和μ子（电子的大质量相对物）的几种罕见衰变模式的准确性提高了大约一个数量级。 在田纳西州橡树岭国家实验室的中子源启动了一个新项目，包括实验“Nab”和“abBA”，目的是同时精确测量中子β衰变的几个衰变参数。 通过它们的精确性，这些实验将探索SM的类似有趣的可能扩展。 在过去的五年中，该计划导致了四个博士学位在UVa。 两个弗吉尼亚大学博士学生们目前正在写论文，计划不久将有第三名学生加入该小组。 每年通常有一到两名本科生参与该项目的研究，从而获得实际的实验室经验。