Scale factor in double parton collisions and parton densities in transverse space

The scale factor sigma (eff)., which characterizes double parton collisions in high energy hadron interactions, is a direct manifestation of the distribution of the interacting partons in transverse space, in such a way that different distributions give rise to different values of sigma (eff) in different double parton collision processes. We work out the value of the scale factor in a few reactions of interest, in a correlated model of the multiparton density of the proton recently proposed.