Lattice QCD Study of Hadron Excitations Using All-to-All Quark Propagators with Improved Variance Reduction

被激发强子共振的质量将通过计算机模拟时空晶格上的夸克和胶子来评估。这些共振态正在几个实验中进行研究，例如在托马斯·杰斐逊国家加速器设施的B厅N*项目和D厅的GlueX实验。这样的系统还应该提供丰富的信息，以帮助我们理解量子色动力学中的夸克约束和强子形成的物理学，强相互作用理论和自然的基本力量之一。理解约束胶子的物理学是一个重要的智力挑战；事实上，它是由马萨诸塞州剑桥克莱数学研究所宣布的所谓的七个千禧年奖问题之一。研究这类系统最可靠的方法之一是使用时空晶格上定义的夸克和胶子场的马尔可夫链蒙特卡罗计算。在过去，由于计算的限制，这样的计算是用不切实际的大夸克质量完成的。目前的计算已经将夸克质量降低到接近其物理值，这使得将多强子算符纳入计算变得至关重要。近年来，一种处理多强子算子的新方法已经发展起来，本提案计划将新方法应用于使用单强子算子和多强子算子进行强子质量的首次计算。拟议的研究包括两名研究生，可能还有一名或多名本科生的参与，他们的教育将不仅通过参与核理论前沿的科学项目而得到加强，而且还将通过使用最先进的并行计算资源的高科技培训得到加强。拟议活动的广泛影响将通过在可公开访问的网页上公布附有简化背景资料的结果而得到加强。

The masses of excited hadron resonances will be evaluated using computer simulations of quarks and gluons on a space-time lattice. These resonance states are being studied in several experiments, such as in the Hall B N* program and the GlueX experiment in Hall D at the Thomas Jefferson National Accelerator Facility. Such systems should also provide a wealth of information to help us understand the physics of quark confinement and hadron formation in quantum chromodynamics, the theory of the strong interactions and one of the fundamental forces of Nature. Understanding the physics of confining gluons is an important intellectual challenge; in fact, it is one of the seven so-called Millenium Prize problems announced by the Clay Mathematics Institute of Cambridge, Massachusetts. One of the most reliable means of investigating such systems is using Markov-chain Monte Carlo computations with quark and gluon fields defined on a space-time lattice. In the past, such calculations have been done with unrealistically large quark masses due to computational limitations. Current calculations have reduced the quark masses to nearly their physical values, causing the need to incorporate multi-hadron operators into the computations to become crucial. A new methodology for dealing with multi-hadron operators has been developed in the recent past, and this proposal plans to apply the new methodology to carry out the first calculations of the hadron masses using both single and multi-hadron operators. The proposed research incorporates the participation of two graduate students, and possibly one or more undergraduate students, whose educations will be enhanced not only by involvement in scientific projects at the forefront of nuclear theory, but also with high-technology training in the use of state-of-the-art parallel computing resources. The broader impacts of the proposed activities will be strengthened by posting results with simplified background information on publicly accessible web pages.