New Perspectives on Bound States and the Flavor Problem

关于束缚态和风味问题的新视角

• 批准号: 1068286
• 负责人: Richard Lebed
• 金额: $ 60万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1068286&HistoricalAwards=false
• 关键词: New; Perspectives; Bound; States; Flavor

With the progress of science, the previously distinct disciplines of nuclear physics, elementary particle physics, astrophysics, and cosmology are becoming ever more closely intertwined. This award, while nominally categorized under nuclear theory because of its focus on the structure and dynamics of subnuclear particles, also contains strong elements of particle theory, atomic physics, and even string theory. In order to reflect not only the wide interests of the PI and co-PI, but also to provide their Ph.D. students a wide range of exciting research opportunities, the project covers five distinct areas of study in which rapid progress is attainable. The award also provides some support for short-term visitors (collaborators and seminar speakers), whose expertise will stimulate further advances in the project areas, and travel funds for all personnel to present their findings at seminars and conferences and to learn about new advances in physics. The broader significance of this project is thus incorporated in (i) interdisciplinary research that crosses boundaries between fields, (ii) the training of junior researchers in the methods and findings these disciplines, and (iii) cross-institutional exchanges to maximize the effectiveness of all involved researchers' skills. The five topics are: (1) Baryons, such as protons and neutrons, can be studied by allowing the number of charges (Nc) of the strong nuclear force to vary. The "1/Nc expansion" is based on the idea that the structure and dynamics of baryons are easier to understand if Nc is considered a large number (it is 3 in our universe). But recent work shows that the expansion is not unique. The PI will compare the predictions of different 1/Nc expansions using experimental data to determine which, if any, is preferred. (2) Generalized parton distributions are the most fundamental observable quantities for describing the structure of strongly-interacting particles such as protons. The upgrade at Jefferson Lab in Newport News, Virginia makes it possible to measure them with unprecedented accuracy, so the calculation of corrections to the older "low-order" results by the co-PI will be essential to our determination of whether one really understand what is going on inside a proton. (3) Protons are sensitive not only to the strong nuclear force, but the weak force as well through the process of "electroweak deep inelastic scattering" (EW DIS), and these effects will appear not only in data at Jefferson Lab, but also subsequent facilities. The co-PI will calculate corrections to the lowest-order results, which will allow one to understand how multiparticle states are correlated at long distance and to separate known from as-yet-unknown physics. (4) Both the PI and co-PI will study the origin of how different species of neutrinos, extremely light and electrically neutral particles, can transform into each other. They will employ both conventional symmetry approaches within the context of quantum field theory and string-theoretical approaches based upon the idea that particles arise from structures called "D-branes" that live in extra dimensions of spacetime but intersect with our dimensions. (5) The PI will build on his recent work describing how to create "true muonium" - an atom consisting of a muon (a subatomic particle created, for example, in cosmic rays) and its antiparticle, in immediately realizable experiments. Like all atoms, it appears in a multitude of excited states with a rich spectroscopy, and how to create and characterize these states is interesting not only for its own sake but for precision tests of the electromagnetic forces that bind the true muonium atom.

随着科学的进步，核物理、基本粒子物理、天体物理和宇宙学等原本截然不同的学科正变得更加紧密地交织在一起。该奖项虽然名义上被归类为核理论，因为它专注于亚核粒子的结构和动力学，但也包含了粒子理论、原子物理甚至弦理论的强大元素。为了不仅反映国际和平协会和联合国际组织的广泛兴趣，也为了给他们的博士生提供广泛的令人兴奋的研究机会，该项目涵盖了五个可以迅速取得进展的不同研究领域。该奖项还为短期参观者(合作者和研讨会演讲者)提供一些支持，他们的专业知识将促进项目领域的进一步进展，并为所有人员在研讨会和会议上介绍他们的发现和了解物理学的新进展提供旅费。因此，该项目的更广泛意义体现在：(I)跨领域的跨学科研究，(Ii)对初级研究人员进行关于这些学科的方法和结果的培训，(Iii)跨机构交流，以最大限度地发挥所有相关研究人员的技能。这五个主题是：(1)重子，如质子和中子，可以通过改变强核力的电荷数(Nc)来研究。“1/Nc展开”是基于这样一种想法，即如果Nc被认为是一个大数字(它在我们的宇宙中是3)，那么重子的结构和动力学更容易理解。但最近的研究表明，这种扩张并不是唯一的。PI将使用实验数据比较不同1/NC展开的预测，以确定哪一种(如果有的话)是首选的。(2)广义部分子分布是描述质子等强相互作用粒子结构的最基本的可观测量。弗吉尼亚州纽波特纽波特纽斯的杰斐逊实验室的升级使以前所未有的精度测量它们成为可能，因此，联合PI对较旧的“低阶”结果的修正计算将对我们确定是否真的理解质子内部发生的事情至关重要。(3)质子不仅对强核力敏感，而且通过“电弱深非弹性散射”(EW DIS)过程对弱核力敏感，这些效应不仅会出现在Jefferson实验室的数据中，而且还会出现在后续的设施中。Co-pi将计算对最低阶结果的修正，这将使人们能够理解多粒子状态是如何在远距离关联的，并将已知和未知的物理分开。(4)PI和co-PI都将研究不同种类的中微子--极轻和电中性粒子--如何相互转化的起源。他们将在量子场论的背景下使用传统的对称性方法，以及弦理论方法，该方法基于这样的想法，即粒子来自于时空中额外维度但与我们的维度相交的被称为D-膜的结构。(5)PI将以他最近的工作为基础，描述如何在可立即实现的实验中创造“真正的Muonium”--一种由Muon(例如，在宇宙射线中产生的亚原子粒子)及其反粒子组成的原子。像所有的原子一样，它以丰富的光谱出现在多种激发态中，如何创建和表征这些态不仅是为了它本身，也是为了精确测试束缚真正的钚原子的电磁力。