Investigating the puzzle of scalar mesons in QCD and their connections to nonperturbative Higgs dynamics

该奖项提供旅行资金和计算资源，用于研究低于2gigaelectronvolts的标量介子的性质和夸克子结构及其对低能量子色动力学（QCD）相关问题的影响。关于最轻的标量介子，一个众所周知但又十分令人困惑的现象是，包含奇异夸克和非奇异夸克的态的质量排序似乎是相反的：假定的K_0^*（800）介子（包含一个奇异夸克）比a_0（980）介子（只包含非奇异夸克）轻。这导致了这样的猜测，即这些标量介子主要是四夸克态，而不是夸克-反夸克态。这项研究将涉及在强耦合制度和解释奇异态的双夸克和四夸克的不同近似方案进行比较。该方法将是来自手征Langrangian的有效场论的方法，其参数将从SLAC的粒子数据组出版物中发现的实验数据确定。已从实验数据构建的分波振幅将用于确定双夸克方法以及不同的么正化方案的有用性。利用这些方法，可以从理论上更好地理解低质量标量介子的性质。 更广泛的影响是，希望通过更好地理解较低能量的标量介子，人们将对标准模型中的非微扰希格斯动力学有一些了解。我们也希望这一分析能有助于理解BaBar合作中的重介子衰变。PI将使他的研究在他的机构的本科生参与他的研究项目的各个方面。

This award provides travel funds and computational resources toward the project objective of investigating the properties and the quark substructure of the scalar meson below two gigaelectronvolts and their impacts on related issues in low-energy Quantum Chromodynamics (QCD). A well-known, and quite puzzling, aspect of the lightest scalar mesons is that there seems to be a reverse mass ordering of states containing strange and non-strange quarks: the putative K_0^*(800) meson (with a strange quark) is lighter than the a_0(980) meson (containing solely non-strange quarks). This has led to the speculation that these scalar mesons are predominantly tetraquark, and not quark-antiquark states. The research will involve comparing different approximation schemes in strongly coupled regimes and interpreting exotic states in terms of diquarks and tetra quarks. The approach will be the method of effective field theories coming from chiral Langrangians whose parameters will be determined from experimental data found in the Particle Data Group publication from SLAC. Partial wave amplitudes that have been constructed from experimental data will be used to determine the usefulness of the diquark approach as well as different unitarization schemes. Using these methods the properties of the low mass scalar mesons will be better understood theoretically. The broader impacts are that it is hoped by better understanding the lower energy scalar mesons one will get some insight into the non-perturbative Higgs dynamics in the Standard Model. It is also hoped that this analysis can be helpful in understanding the decay of heavier mesons by the BaBar collaboration. The PI will make his research accessible for the undergraduates at his institution to take part in various aspects of his research project.