Research on the coupling constant and its scale dependence via lattice QCD simulations

本研究的目的之一是通过格点QCD模拟计算QCD中的基本参数之一耦合常数的尺度依赖性。我们对胶子采用RG改进的规范作用量，对夸克采用非微扰改进的Wilson费米子作用量。通过薛定谔泛函方法计算了耦合常数的阶跃标度函数，以评估耦合常数的标度依赖性。作为第一步，边界项的改进系数确定在1圈微扰理论的情况下的RG规范作用。在淬火QCD模拟中测试了该系数的确定。然后，我们已经确定了三叶草系数的费米子作用的非微扰薛定谔功能设置中的改进项。此外，重整化常数以及各种运营商的改进系数估计的薛定谔泛函方法。另一方面，为了确定低能标度，我们在2 + 1味全QCD模拟中计算了强子谱。本文提出了一种新的理论方法--Wilson手征微扰理论，用来控制Wilson型夸克的手征外推，并利用这种方法计算了各种量的夸克质量依赖性。我们已经测试了一个新的算法，轻动力学夸克，称为域分解HMC算法，对格点QCD模拟在物理夸克质量。目前正在对3味QCD中的SSF进行评估，并对2 + 1味QCD中的强子谱进行计算。

A purpose of this project is to calculate a scale dependence of the coupling constant, which is one of fundamental parameters in QCD, by lattice QCD simulations. We use a RG improved gauge action for gluons and a non-perturbatively improved Wilson fermion act ion for quarks. A step scaling function of the coupling constant is calculated by the Schrodinger functional method to evaluate the scale dependence of the coupling constant. As a first step, an improvement coefficient for a boundary term is determined at 1 loop in perturbation theory for a case of the RG gauge act ion. This determination of the coefficient is tested in quenched QCD simulations. We then have determined the clover coefficient for an improved term in the fermion action non-perturbatively in the Schrodinger functional setup. In addition, renormalization constants as well as improved coefficients for various operators are estimated by the Schrodinger functional method. On the other hand, we have calculated hadron spectra in 2+1 flavor full QCD simulations, in order to determine a low energy scale. A new theoretical method, called Wilson chiral perturbation theory, is proposed to control chiral extrapolations for Wilson type quarks and quark mass dependences for various quantities are calculated by this method. We have tested a new algorithm for light dynamical quarks, called domain-decomposed HMC algorithm, towards lattice QCD simulations at physical quark mass. An evaluation of SSF in 3 flavor QCD and a calculation of hadron spectra in 2+1 flavor QCD are now under way.