Fundamental Studies of the Nucleon Spin in QCD

QCD 中核子自旋的基础研究

• 批准号: 0855498
• 负责人: Renee Fatemi
• 金额: $ 47.99万
• 依托单位: University of Kentucky Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0855498&HistoricalAwards=false
• 关键词: Fundamental; Studies; Nucleon; Spin; QCD

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The protons and neutrons that serve as building blocks for our visible universe are constructed from smaller, more fundamental particles called quarks and gluons. These point-like particles, or partons, are confined inside nucleons due to the nature of the strong force which governs their interactions. Consequently, the abundant, stable and easily manipulated proton has served as an experimental "partonic laboratory'' for over half a century. The underlying mechanisms of Quantum Chromodynamics (QCD), the formal theory of strong interactions, are illuminated via investigations into how the proton mass, charge and spin manifest from partonic degrees of freedom.Spin, a type of angular momentum inherent to all fundamental particles, is a purely quantum mechanical dynamic and therefore serves as a particularly sharp probe into the nature of QCD. The "spin puzzle" is an outstanding question in QCD physics and can be stated simply: How does the spin and orbital angular momentum of the quarks and gluons combine to form the total proton spin of 1/2? Two decades of experiments have constrained the total quark spin contribution to be about 1/3 of the sum. This surprisingly small value motivates experiments designed to measure the flavor-separated quark spin distributions as well as the gluon spin and partonic orbital angular momentum pieces of the spin puzzle.This award will fund experimental efforts to constrain the gluon contribution to the spin puzzle via measurements of jet asymmetries as reconstructed in the STAR detector at the Relativistic Heavy Ion Collider. These funds will also support manpower for the construction, testing and installation of the data acquisition system for the Forward Gem Tracker, the STAR detector upgrade designed to measure the parity violating asymmetries of W production that are sensitive to the flavor separated anti-up and anti-down quark spin distributions in the proton. This award provides the unique opportunity for University of Kentucky graduate and undergraduate students to learn and develop the software tools and analysis techniques necessary for jet reconstruction, while simultaneously contributing to the construction of a state-of-the-art detector at the worlds only high-energy polarized proton collider.

该奖项是根据 2009 年美国复苏和再投资法案（公法 111-5）资助的。作为我们可见宇宙的基石的质子和中子是由更小、更基本的粒子（称为夸克和胶子）构成的。 由于控制它们相互作用的强力的性质，这些点状粒子或部分子被限制在核子内部。 因此，半个多世纪以来，丰富、稳定且易于操纵的质子一直充当着实验性的“粒子实验室”。通过研究质子质量、电荷和自旋如何从粒子自由度中表现出来，量子色动力学（QCD）这一强相互作用的形式理论的基本机制得到了阐明。自旋是所有基本粒子固有的一种角动量，是一种纯粹的量子理论。 机械动力学，因此可以作为对 QCD 本质的特别尖锐的探索。 “自旋难题”是QCD物理学中的一个突出问题，可以简单地表述为：夸克和胶子的自旋和轨道角动量如何结合形成1/2的总质子自旋？ 二十年的实验已经将夸克自旋的总贡献限制在总和的 1/3 左右。 这个令人惊讶的小值激发了实验的兴趣 旨在测量风味分离的夸克自旋分布以及自旋谜题的胶子自旋和部分子轨道角动量部分。该奖项将资助通过测量相对论重离子对撞机的 STAR 探测器中重建的射流不对称性来限制胶子对自旋谜题的贡献的实验工作。 这些资金还将支持数据采集系统的建设、测试和安装的人力 对于前向宝石追踪器，STAR 探测器升级旨在测量 W 产生的宇称破坏不对称性，这些不对称性对质子中风味分离的反上夸克和反下夸克自旋分布敏感。该奖项为肯塔基大学研究生和本科生提供了独特的机会来学习和开发射流重建所需的软件工具和分析技术，同时为最先进的探测器的构建做出贡献 在世界上唯一的高能偏振质子对撞机上。