Clover improvement for stout-smeared 2+1 flavour SLiNC fermions: perturbative results

格鲁宁双线算符在具有斯图特-模糊链接的格点SYM中的微调与重整化

Fine-tunings and renormalization of gluino bilinear operators in lattice SYM with Stout-Smeared links

本文通过改进的格点动作计算了SYM理论中胶子和胶子双线算符的重整化因子，并确定了确保轴电流守恒的smearing参数。

Renormalization of Flavor Singlet and Nonsinglet Fermion Bilinear Operators

We compute the difference in the renormalization of flavor singlet and nonsinglet fermion bilinear operators, to two loops in perturbation theory. Our results are applicable to a rather wide class of lattice actions with Symanzik improved gluons, stout links and clover fermions, including the Twisted Mass and SLiNC actions. A more detailed presentation of our results, along with relevant references, will appear in a forthcoming publication.

Perturbative determination of $c_{SW}$ with Symanzik improved gauge action and stout smearing

We determine the improvement factor $c_{SW}$ in one-loop lattice perturbation theory for the plaquette and Symanzik improved gauge actions. The fermionic action is ${\mathcal{O}(a)}$ clover improved with one-time stout smearing. $c_{SW}$ is derived from the one-loop correction to the quark-quark-gluon vertex in the off-shell regime. We give a first numerical value for the one-loop contribution to the non gauge-invariant improvement coefficient $c_{NGI}$ for the quark field using the plaquette action. A discussion of mean field improvement is included.

Non-perturbative evaluation of cSW for smeared link clover fermion and Iwasaki gauge action

We performed a rough estimate of the non-perturbative value of the clover term coefficient cSW for the APE stout link Wilson fermion. We varied the number of smearings from Nsmear=1 to 6 and adopted beta values roughly corresponding to the lattice spacing of 0.1 fm. We used the Schroedinger functional technique for an evaluation of cSW and found that cSW decreases monotonically as we increase Nsmear but has a 10% order of deviation from the tree level value for Nsmear=6.

格点微扰理论中的 stout smearing 与 Wilson flow

Stout smearing and Wilson flow in lattice perturbation theory

本文在格点微扰理论中将 stout smearing 与 Wilson flow 展开至 $g_0^3$ 阶，阐明二者通过极限相互关联，并用于任意格点费米子作用量的 Feynman 规则及 clover 改进 Wilson 费米子自能计算。

Parameter Tuning of Three-Flavor Dynamical Anisotropic Clover Action

In this work, we perform parameter tuning with dynamical anisotropic clover lattices using the Schrödinger functional and stout-smearing in the fermion field. We find that $ξ_R/ξ_0$ is relatively close to 1 in our parameter search, which allows us to fix $ξ_0$ in our runs. We proposed to determine the gauge and fermion anisotropy in a Schrödinger-background small box using Wilson loop ratios and PCAC masses. We demonstrate that these ideas are equivalent to but more efficient than the conventional meson dispersion approach. The spatial and temporal clover coefficients are fixed to the tree-lev…

Scaling study of dynamical smeared-link clover fermions

We present a framework for phenomenological lattice QCD calculations which makes use of a tree level Symanzink improved action for gluons and stout-link Wilson fermions. We give details of our efficient HMC/RHMC algorithm and present a scaling study of the low-lying N_f=3 baryon spectrum. We find a scaling region that extends to a~<0.16fm and conclude that our action and algorithm are suitable for large scale phenomenological investigations of N_f=2+1 QCD. We expect this conclusion to hold for other comparable actions.

Isovector charges of the nucleon from 2+1-flavor QCD with clover fermions

We present high-statistics estimates of the isovector charges of the nucleon from four 2+1-flavor ensembles generated using Wilson-clover fermions with stout smearing and tree-level tadpole improved Symanzik gauge action at lattice spacings $a=0.114$ and $0.080$ fm and with $M_π\approx 315$ and 200 MeV. The truncated solver method with bias correction and the coherent source sequential propagator construction are used to cost-effectively achieve $O(10^5)$ measurements on each ensemble. Using these data, the analysis of two-point correlation functions is extended to include four states in the f…

Improving the lattice axial vector current

For Wilson and clover fermions traditional formulations of the axial vector current do not respect the continuum Ward identity which relates the divergence of that current to the pseudoscalar density. Here we propose to use a point-split or one-link axial vector current whose divergence exactly satisfies a lattice Ward identity, involving the pseudoscalar density and a number of irrelevant operators. We check in one-loop lattice perturbation theory with SLiNC fermion and gauge plaquette action that this is indeed the case including order $O(a)$ effects. Including these operators the axial Ward…

采用改进离散化的超对称杨-米尔斯理论（SYM）中诺特定理流的微扰重整化

Perturbative Renormalization of Noether Currents in SYM with Improved Discretizations

本文研究采用改进离散化的$\boldsymbol{\textit{N}=1}$超对称杨-米尔斯理论中诺特定理流的微扰重整化，计算了超流的一圈阶重整化因子与混合系数，为格点模拟恢复超对称提供指导。

Tuning improved anisotropic actions in lattice perturbation theory

We discuss the tuning of the anisotropic clover action and Symanzik-improved gauge action in lattice perturbation theory. The fermion action is constructed from stout-smeared spatial links, which complicates the calculation considerably. In addition, the full quark-mass dependence of the action parameters is included in this study. We present results for the fermion and gauge aspect ratios for varying bare aspect ratios, quark masses and smearing parameters.

Approaching the conformal window: systematic study of the particle spectrum in SU(2) field theory with Nf=2, 4 and 6

It is expected that SU(2) gauge theory with $N_f$ fundamental fermions has an infrared fixed point when $N_f$ is between $\sim 6$ and 10. We study the hadron spectrum and scale setting in SU(2) gauge field theory with $N_f=2,4,6$ using hypercubic stout smeared Wilson-clover (HEX) action. The case $N_f=2$ is QCD-like, whereas $N_f=6$ is close to the lower edge of the conformal window. In our study the length scales are determined by using the gradient flow approach.

基于蝌蚪改进的clover系综在连续极限下的夸克质量与低能常数

Quark masses and low energy constants in the continuum from the tadpole improved clover ensembles

本研究基于2+1味全QCD蝌蚪改进clover系综，通过PCAC关系和RI/MOM方案精确测定了轻夸克质量及低能常数，并全面评估了系统误差。

Improved renormalization scheme for nonlocal operators

In this paper we present an improved RI-type prescription appropriate for the non-perturbative renormalization of gauge invariant nonlocal operators. In this prescription, the non-perturbative vertex function is improved by subtracting unwanted finite lattice spacing ($a$) effects, calculated in lattice perturbation theory. The method is versatile and can be applied to a wide range of fermion and gluon actions, as well as types of nonlocal operators. The presence of operator mixing can also be accommodated. Compared to the standard RI' prescription, this variant can be recast as a supplementar…

使用扭转质量费米子计算质子的胶子部分子分布函数（Gluon PDF）

Gluon PDF of the proton using twisted mass fermions

本研究利用格点QCD的赝分布方法，基于N_f=2+1+1最大扭转质量费米子系综计算质子非极化胶子PDF，探究多种系统效应，首次通过扩展夸克单态数据集消除了胶子PDF与夸克单态的混合。