Renormalization of quark bilinear operators in a MOM-scheme with a non-exceptional subtraction point

We extend the Rome-Southampton RI/MOM renormalization scheme for bilinear operators to one with a non-exceptional, symmetric subtraction point. Two-point Green’s function with the insertion of quark bilinear operators are computed with scalar, pseudo-scalar, vector, axial-vector and tensor operators at one-loop order in perturbative QCD. Conversion factors are derived, which connect this RI/SMOM-scheme and the MS-scheme and can be used to convert results obtained in lattice calculations into the MS-scheme. Such a symmetric subtraction point involves non-exceptional 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 infra-red improved kinematics is substantially decreased in the case of the pseudo-scalar 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.