Experimental Studies of Broken Symmetries with Muons, Pions and Photons

μ子、π介子和光子破缺对称性的实验研究

• 批准号: 0072200
• 负责人: Tim Gorringe
• 金额: $ 40.86万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-06-01 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0072200&HistoricalAwards=false
• 关键词: Experimental; Studies; Broken; Symmetries; Muons

0072200Gorringe Quantum chromodynamics (QCD) is the accepted theory of thestrong interactions of quarks and gluons. At low energies the quarksand gluons are confined in baryons (three quarks) and mesons(quark--antiquark pairs), and understanding the properties andinteractions of baryons and mesons in terms of QCD is of fundamental importance. QCD possess a number of elementary symmetries. They include isospin symmetry, whereby the interactions are unaltered by u,d quark flavor rotations, and chiral symmetry, whereby the interactions are unaltered by separate flavor rotations for left, right handed quarks. The realization of these symmetries is rich and varied, involving so-called spontaneous, explicit and anomalous symmetry breaking effects. Understanding their realization is central to understanding the low energy interactions of baryons and mesons. This experimental research addresses the manifestation of symmetries in low energy processes. At the TRIUMF Laboratory in Vancouver, Canada we are investigating chiral and isospin symmetries with beams of muons and pions. For example the weak interaction between muons and protons is a key test of chiral symmetry breaking and the strong interaction between pions and protons is central to understanding the breaking of isospin. In addition, at the Jefferson Laboratory in Newport News, Virginia we are collaborating on a precision measurement of the decay rate of the neutral pion - a unique test of anomalous symmetry breaking in QCD.

0072200Gorringe 量子色动力学（QCD）是夸克和胶子强相互作用的公认理论。在低能量下，夸克和胶子被限制在重子（三夸克）和介子（夸克-反夸克对）中，从 QCD 角度理解重子和介子的性质和相互作用至关重要。 QCD 具有许多基本对称性。 它们包括同位旋对称性和手性对称性，其中相互作用不被u、d夸克风味旋转改变，而手性对称性则相互作用不被左、右手夸克单独的风味旋转改变。 这些对称性的实现是丰富多样的，涉及所谓的自发的、显性的和反常的对称破缺效应。 了解它们的实现对于理解重子和介子的低能相互作用至关重要。这项实验研究解决了低能量过程中对称性的表现。在加拿大温哥华的 TRIUMF 实验室，我们正在研究 μ 介子和介子束的手性和同位旋对称性。例如，μ介子和质子之间的弱相互作用是手性对称性破缺的关键测试，介子和质子之间的强相互作用是理解同位旋破缺的核心。此外，在弗吉尼亚州纽波特纽斯的杰斐逊实验室，我们正在合作精确测量中性π介子的衰变率，这是对 QCD 反常对称性破缺的独特测试。