Non-perturbative renormalization in coordinate space for $N_f=2$   maximally twisted mass fermions with tree-level Symanzik improved gauge   action
  We present results of a lattice QCD application of a coordinate space renormalization scheme for the extraction of renormalization constants for flavour non-singlet bilinear quark operators. The method consists in the analysis of the small-distance behaviour of correlation functions in Euclidean space and has several theoretical and practical advantages, in particular: it is gauge invariant, easy to implement and has relatively low computational cost. The values of renormalization constants in the X-space scheme can be converted to the MSbar scheme via 4-loop continuum perturbative formulae. Our results for $N_f=2$ maximally twisted mass fermions with tree-level Symanzik improved gauge action are compared to the ones from the RI-MOM scheme and show full agreement with this method. 
Krzysztof Cichy, Karl Jansen, Piotr Korcyl
hep-lat