  We investigate the azimuthal asymmetry v2 of produced pions in pp and pA
collisions at both RHIC and SPS energies. In our approach, based on the pQCD
parton model and the light-cone QCD-dipole formalism, the azimuthal asymmetry
results from a correlation between the color-dipole orientation and the impact
parameter of the collision. We introduce the color-dipole orientation within an
improved Born approximation and the saturation model which satisfies available
DIS data, showing that the azimuthal asymmetry of partons and pions is very
sensitive to the choice of the model, and that it is reduced in the saturation
model. We find that v2 of quarks and gluons in parton-nucleus collisions have
very different patterns. The azimuthal asymmetry of gluons in gluon-nucleus
collisions can be negative at small transverse momentum, changes the sign and
becomes positive at high transverse momentum. The azimuthal asymmetry of quarks
in quark-nucleus collisions is positive at all values of transverse momentum.
We find that the azimuthal anisotropy v2 of produced pions in both pp and pA
collisions is positive, albeit rather small.
