Three loop (MS)over-bar renormalization of the Curci-Ferrari model and the dimension two BRST invariant composite operator in QCD

The massless Curci-Ferrari model with N-f flavours of quarks is renormalized to three loops in the MS scheme in an arbitrary covariant gauge with parameter alpha. The renormalization of the BRST invariant dimension two composite operator, 1/2A(mu)(a2) - alpha(c) over bar (a)c(a), which corresponds to the mass operator in the massive Curci-Ferrari model, is determined by renormalizing the Green's function where the operator is inserted in a ghost two-point function. Consequently the anomalous dimension of the QCD Landau gauge operator, 1/2A(mu)(a2) and the (gauge independent) photon mass anomalous dimension in QED are both deduced at three loops. (C) 2002 Elsevier Science B.V. All rights reserved.