  Making use of the Stochastic Vacuum Model and the gluon gauge-invariant
two-point correlation function, determined by numerical simulation on the
lattice in both quenched approximation and full QCD, we calculate the
elementary (quark-quark) scattering amplitudes in the momentum transfer space
and at asymptotic energies. Our main conclusions are the following: (1) the
amplitudes decrease monotonically as the momentum transfer increases; (2) the
decreasing is faster when going from quenched approximation to full QCD (with
decreasing quark masses) and this effect is associated with the increase of the
correlation lengths; (3) dynamical fermions generate two components in the
amplitude at small momentum transfer and the transition between them occurs at
momentum transfer near 1 GeV$^2$. We also obtain analytical parametrizations
for the elementary amplitudes, that are suitable for phenomenological uses, and
discuss the effects of extrapolations from the physical regions investigated in
the lattice.
