QCD Parameters

QCD参数

• 批准号: 261334331
• 负责人: Professor Dr. Hubert Spiesberger
• 金额: --
• 依托单位: Institut für Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/261334331?language=en
• 关键词: QCD; Parameters

Goal of this project is a timely determination of the fundamental parameters of quantum chromodynamics (QCD). New experimental measurements with high precision and new results from calculations of higher orders in perturbative QCD allow us to test our understanding of the theory of the strong interaction with higher accuracy and with more reliability. The higher precision also allows one to discover indirect hints for new physics from the observation of discrepancies between present day's experiments and theoretical predictions. Obviously, such an ambitious goal requires a precise knowledge of the parameters of the underlying theory. One of the most important parameters, the strong coupling constant, alphas, was and still is subject of extensive investigations. One of the most precise determinations of alphas relies on the knowledge of the total decay rate of tau leptons. Despite of the fact that higher-order corrections from perturbative QCD have been calculated to order alphas^4, different prescriptions for the resummation of leading logarithms by an application of the renormalization group equation can lead to differing results. The precision of such calculations is therefore not fully understood. In the proposed research project we want to study an approach to QCD adapted from similar investigations in the Standard Model of electroweak interactions. Instead of using alphas as expansion parameter of the perturbative series we want to use the decay rate of the $\tau$ lepton. This way, the perturbative expansion would become independent of the renormalization schemes and renormalization scales. Subject of the proposed research will also be other important parameters of QCD, in particular the masses of the u and d quarks, and the gluon condensate. Many previous attempts to determination quark masses were based on QCD sum rules, or on lattice QCD. Each of these approaches have their pro's and con's and it is important to perform alternative calculations in order to establish a consistent picture. The authors of this research proposal have developped, partly in collaboration with other groups of researchers, their own techniques for the application of QCD sum rules. With the help of these techniques it will be possible to extract precise information about QCD parameters and compare experimental results with theoretical predictions. The research program described in this proposal is planned for a collaboration between members of the University of Mainz and the group of Professor C. A. Dominguez at the University of Cape Town. Both groups work in the same field of the application of QCD to low-energy particle physics. The young South African scientists participating in the project come from population groups which were under-privileged under the Apartheid Regime.

该项目的目标是及时确定量子色动力学的基本参数。新的高精度实验测量和摄动QCD中高阶计算的新结果使我们能够以更高的精度和更高的可靠性测试我们对强相互作用理论的理解。更高的精度还允许人们通过观察目前的实验和理论预测之间的差异来发现新物理学的间接线索。显然，这样一个雄心勃勃的目标需要对基础理论的参数有精确的了解。最重要的参数之一，强耦合常数，阿尔法，过去是，现在仍然是广泛研究的主题。最精确的测定之一依赖于对tau轻子总衰变率的了解。尽管摄动QCD的高阶修正已被计算为阶α ^4，但通过应用重整化群方程恢复前导对数的不同处方可能导致不同的结果。因此，这种计算的精度还不完全清楚。在提议的研究项目中，我们希望研究一种基于电弱相互作用标准模型中类似研究的QCD方法。而不是用作为微扰级数的展开参数我们想用轻子的衰减率。这样，微扰展开就与重整化方案和重整化尺度无关。提出的研究主题也将是QCD的其他重要参数，特别是u和d夸克的质量，以及胶子凝聚。以前许多确定夸克质量的尝试都是基于QCD和规则，或者基于点阵QCD。每种方法都有其优点和缺点，为了建立一致的图像，执行替代计算是很重要的。这项研究计划的作者已经开发了他们自己的技术，部分是与其他研究小组合作，用于应用QCD求和规则。在这些技术的帮助下，将有可能提取有关QCD参数的精确信息，并将实验结果与理论预测进行比较。本提案中描述的研究项目计划由美因茨大学成员和开普敦大学C. a . Dominguez教授小组合作进行。这两个小组都在同一个领域工作，将QCD应用于低能粒子物理。参与该项目的年轻南非科学家来自种族隔离制度下的弱势群体。