TWIST - Precision measurement of muon decay parameters (TRIUMF E614)

TWIST - μ子衰变参数的精密测量 (TRIUMF E614)

• 批准号: 186695-2007
• 负责人: Marshall, Glen
• 金额: $ 19.67万
• 依托单位: TRIUMF
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=365759
• 关键词: TWIST; Precision; measurement; muon; decay

The TRIUMF Weak Interaction Symmetry Test (TWIST) is a search for tiny deviations from the pattern ofmuon decays predicted by the very successful Standard Model of particle interactions. The Standard Model, atheory which agrees with many observations over many years, is nonetheless believed by most subatomicphysicists to be only an approximation to a more basic and precise model whose properties are as yet notknown. The Standard Model is incomplete and leaves several questions unanswered, for example, why justthree generations, and why do the particles have the masses they do?The Standard Model classifies the most fundamental particles into three "generations"; only particles of thefirst or lowest generation make up the materials of our everyday lives. The muon is the lightest and mostaccessible fundamental charged particle of a higher generation. It nearly always decays into an electron and twovery light, elusive, neutral particles called neutrinos. High quality beams of muons are produced at TRIUMF,and a very high precision detector system in a high solenoidal magnetic field is used to accurately measure thedirection and energy of the positive electron (or positron) produced for each of billions of positive decays. Thepattern or symmetry of these decays is precisely predicted by the Standard Model.If found, a deviation from expectations based on the Standard Model would provide clues to the character of amore basic description of the smallest particles in our universe. On the other hand, if no deviation is found,some hypothesized features of a more basic description can be eliminated from consideration.

TRIUMF弱相互作用对称测试（TWIST）是一个寻找非常成功的粒子相互作用标准模型所预测的μ子衰变模式的微小偏差。标准模型是一个与多年来的许多观测相一致的理论，然而，大多数亚原子物理学家认为，它只是一个更基本、更精确的模型的近似值，其性质尚不清楚。标准模型是不完整的，有几个问题没有得到解答，例如，为什么只有三代，为什么粒子有这样的质量？标准模型将最基本的粒子分为三代；只有第一代或最低代的粒子才构成我们日常生活的材料。介子是上一代最轻、最容易接近的基本带电粒子。它几乎总是衰变成一个电子和两个非常轻、难以捉摸的中性粒子——中微子。高质量的μ子光束在TRIUMF产生，一个非常高精度的探测器系统在一个高螺线管磁场被用来精确测量正电子（或正电子）的方向和能量产生数十亿的正衰变。标准模型精确地预测了这些衰变的模式或对称性。如果被发现，基于标准模型的预期偏差将为我们了解宇宙中最小粒子的更基本描述的特征提供线索。另一方面，如果没有发现偏差，则可以从考虑中消除更基本描述的一些假设特征。