Anomalous dimension of non-singlet quark currents at O(1/Nf^2) in QCD

Abstract

We compute the O(1/Nf^2) corrections to the flavour non-singlet quark bilinear currents in QCD in arbitrary spacetime dimensions. Hence, the anomalous dimension of the QED current $\bar{\psi} \sigma^{\mu\nu} \psi$ is deduced at four loops in the MSbar scheme up to one unknown parameter.