Hadron Resonances and Exotic States using Lattice QCD with the Stochastic LapH Method

构成原子核的质子和中子是由夸克和胶子这两种基本粒子组成的，它们之间的相互作用可以用量子色动力学（QCD）来描述。这一理论表明，许多其他类型的复合粒子，如强子，应该以不稳定共振的形式存在于自然界中。我们将研究QCD所预测的受激强子共振的性质。外来粒子，如胶球、杂化介子和四夸克是特别有趣的。这项提议的研究为目前正在进行的实验提供了支持，比如在托马斯·杰斐逊国家加速器设施（JLab）的B厅N*项目和D厅的GlueX实验，这些实验正在研究这种强子共振。强子散射也将被研究。这些计算在很大程度上依赖于由NSF支持的极限科学与工程发现环境（XSEDE）提供的资源。拟议的研究包括一名研究生的参与，他的教育不仅将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。激发强子的物理将被研究使用蒙特卡洛估计路径积分涉及夸克和胶子场在时空晶格上。除了传统的介子和重子，胶球和所谓的杂化介子和重子，其中价夸克被激发的胶子场束缚。奇异的插值算子，包括四夸克算子，将被用来探索量子色动力学中激发态的本质。π介子、介子和核子介子散射相移将被计算并用于确定各种共振的衰变宽度，例如介子和Roper和Lambda（1405）共振。一种处理多强子算子的新方法，被称为随机LapH方法，将用于这些计算。新发现的XYZ介子，其成分被认为是由一个重夸克和反夸克加上一个轻夸克和反夸克组成的，将使用传统的点阵QCD技术和Born-Oppenheimer处理来研究。

Protons and neutrons, which make up atomic nuclei, are made up of fundamental particles known as quarks and gluons, whose interactions are described by quantum chromodynamics (QCD). This theory suggests that many other types of composite particles, known as hadrons, should exist in Nature as unstable resonances. The properties of excited hadronic resonances as predicted by QCD will be investigated. Exotic particles, such as glueballs, hybrid mesons, and tetraquarks are of particular interest. The proposed research lends support to current experiments, such as in the Hall B N* program and the GlueX experiment in Hall D at the Thomas Jefferson National Accelerator Facility (JLab), which are studying such hadronic resonances. Hadron scattering will also be investigated. These computations rely heavily on resources provided by the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by the NSF. The proposed research incorporates the participation of a graduate student whose education 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 physics of excited hadrons will be studied using Monte Carlo estimates of path integrals involving quark and gluon fields on a space-time lattice. In addition to conventional mesons and baryons, glueballs and so-called hybrid mesons and baryons in which the valence quarks are bound by an excited gluon field will be investigated. Exotic interpolating operators, including tetraquark operators, will be used to explore the nature of the excited states in quantum chromodynamics. Pion-pion, kaon-pion, and nucleon-pion scattering phase shifts will be computed and used to determine the decay widths of various resonances, such as the rho meson and the Roper and Lambda(1405) resonances. A new methodology for dealing with multi-hadron operators, known as the stochastic LapH method, will be used for these calculations. The newly discovered XYZ mesons, whose constituents are believed to consist of a heavy quark and antiquark plus a light quark and antiquark, will be studied using both conventional lattice QCD techniques and using a Born-Oppenheimer treatment.