Lattice artifacts proportional to the quark mass in the QCD running coupling

Abstract

Discretization artifacts proportional to the quark mass can limit the precision of strong-coupling determinations in lattice QCD, especially in the presence of heavy quarks. In this work, we perform a lattice perturbative analysis of such $\mathcal{O}(a m)$ effects in the running coupling by computing its two-loop renormalization factor $Z_g$. Using the background field method together with clover-improved Wilson fermions and Symanzik-improved gauge actions, we determine the mass-dependent components of the relevant two-point Green's functions and obtain the improvement coefficients needed to remove $\mathcal{O}(a m)$ artifacts in mass-independent renormalization schemes. Our results are presented for general values of the number of colors $N_c$, the number of quark flavors $N_f$, and the clover coefficient $c_{\mathrm sw}$, and satisfy all symmetry and consistency constraints. Numerical values are provided for widely used instances of the above gauge actions, allowing improved control of mass-related cutoff effects in high-precision determinations of the strong coupling constant from lattice QCD. Full derivations and extended numerical results can be found in Ref. [arXiv:2503.00463].

Figures (2)

• Figure 1: One-loop fermionic contributions to the background field two-point function. Solid lines denote fermions and wavy lines with a cross denote background gluons.
• Figure 2: Two-loop fermionic contributions to the background field two-point function. Solid lines denote fermions, wavy lines represent gluons, wavy lines with a cross correspond to background gluons, and a solid line with a circle indicates the one-loop fermion mass counterterm.