A model in which the soft collisions of the nucleon are described in terms of
interactions of its two constituents (a quark and a diquark) is proposed. When
adjusted to describe precisely the elastic proton-proton scattering data and
supplemented with the idea of wounded constituents, the model accounts rather
well for the centrality dependence of particle production in the central
rapidity region at RHIC energies.Comment: 8 pages, 4 figures, added references; corrected typo in Eq. (15