GRIBOV NOISE ON THE LATTICE AXIAL CURRENT RENORMALIZATION CONSTANT

We study the influence of Gribov copies, in the Landau gauge, on the l attice renormalisation constant Z(A) of the axial current, obtained fr om a Ward identity on quark state correlation functions, with the Clov er action, in quenched SU(3) gauge theory. A comparison between the ga uge invariant determination of Z(A) and the gauge dependent one is dis cussed. On a 16(3)x32 lattice at beta=6.0 and with K=0.1425, the value s, on a sample of 36 configurations, are Z(A)=1.08(5) (gauge dependent calculation) and Z(A)=1.06(2) (gauge independent calculation). We fin d that the residual gauge freedom associated to Gribov copies induces observable effects, which, at the level of numerical accuracy of our s imulation, ate included in the statistical uncertainty inherent in a M onte Carlo simulation. Doubling the statistics suggests that the fluct uation due to the lattice Gribov ambiguity scales down at least as fas t as a pure statistical error.