Non-perturbative renormalization constants on the lattice from flavour non-singlet Ward identities

By imposing axial and vector Ward identities for flavour-non-singlet currents, we estimate in the quenched approximation the non-perturbative values of combinations of improvement coefficients, which appear in the expansion around the massless case of the renormalization constants of axial, pseudoscalar, vector, scalar non-singlet currents and of the renormalized mass. These coefficients are relevant for the completion of the improvement programme to O(a) of such operators. The simulations are performed with a clover Wilson action non-perturbatively improved.