Renormalization of quark bilinear operators in a momentum-subtraction scheme with a nonexceptional subtraction point

TL;DR

This paper introduces the RI/SMOM scheme, a symmetric momentum-subtraction method for quark bilinear operators, which reduces infrared contamination and improves perturbative convergence in lattice QCD calculations.

Contribution

The paper extends the RI/MOM scheme to a symmetric subtraction point, deriving conversion factors to the MSbar scheme and demonstrating improved perturbative behavior.

Findings

One-loop corrections are significantly smaller with the symmetric scheme.

The scheme reduces infrared contamination in lattice calculations.

Potential for more accurate quark mass determinations.

Abstract

We extend the Rome-Southampton regularization independent momentum-subtraction renormalization scheme(RI/MOM) for bilinear operators to one with a nonexceptional, symmetric subtraction point. Two-point Green's functions with the insertion of quark bilinear operators are computed with scalar, pseudoscalar, vector, axial-vector and tensor operators at one-loop order in perturbative QCD. We call this new scheme RI/SMOM, where the S stands for "symmetric". Conversion factors are derived, which connect the RI/SMOM scheme and the MSbar scheme and can be used to convert results obtained in lattice calculations into the MSbar scheme. Such a symmetric subtraction point involves nonexceptional momenta implying a lattice calculation with substantially suppressed contamination from infrared effects. Further, we find that the size of the one-loop corrections for these infrared improved kinematics is substantially decreased in the case of the pseudoscalar and scalar operator, suggesting a much better behaved perturbative series. Therefore it should allow us to reduce the error in the determination of the quark mass appreciably.