Two loop correction to the Gribov mass gap equation in Landau gauge QCD
  We determine the two loop correction to Gribov's mass gap equation for quantum chromodynamics in the Landau gauge in the MSbar scheme by computing the two loop correction to the horizon condition derived from Zwanziger's local renormalizable Lagrangian which incorporates the Gribov parameter. We verify that with the explicit result, the two loop ghost propagator is enchanced in the infrared. 
J.A. Gracey