Non-perturbative determination of c_V, Z_V and Z_S/Z_P in N_f=3 lattice QCD

We report on non-perturbative computations of the improvement coefficient c_V and the renormalization factor Z_V of the vector current in three-flavour O(a) improved lattice QCD with Wilson quarks and tree-level Symanzik improved gauge action. To reduce finite quark mass effects, our improvement and normalization conditions exploit massive chiral Ward identities formulated in the Schroedinger functional setup, which also allow deriving a new method to extract the ratio Z_S/Z_P of scalar to pseudoscalar renormalization constants. We present preliminary results of a numerical evaluation of Z_V and c_V along a line of constant physics with gauge couplings corresponding to lattice spacings of about 0.09 fm and below, relevant for phenomenological applications.