  We consider proton-nucleus collisions at high energy in the Color Glass
Condensate framework, and extract from the gluon production cross-section the
probabilities of having a definite number of multiple scatterings in the
nucleus. Various properties of the distribution of the number of multiple
scatterings are studied, and we conclude that events in which the momentum of a
hard jet is compensated by many much softer particles on the opposite side are
very unlikely except for extreme values of the saturation momentum. In the same
framework, we also investigate the possibility to estimate the impact parameter
of a proton-nucleus collision, from the measure of the multiplicity of its
final state.
