GRIBOV NOISE ON THE LATTICE AXIAL CURRENT RENORMALIZATION CONSTANT

We study the influence of Gribov copies, in the Landau gauge, on the lattice renormalisation constant Z(A) of the axial current, obtained from a Ward identity on quark state correlation functions, with the Clover action, in quenched SU(3) gauge theory. A comparison between the gauge invariant determination of Z(A) and the gauge dependent one is discussed. On a 16(3)x32 lattice at beta=6.0 and with K=0.1425, the values, 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 find that the residual gauge freedom associated to Gribov copies induces observable effects, which, at the level of numerical accuracy of our simulation, ate included in the statistical uncertainty inherent in a Monte Carlo simulation. Doubling the statistics suggests that the fluctuation due to the lattice Gribov ambiguity scales down at least as fast as a pure statistical error.