  Starting from the light-cone plasma (LCP) distribution of gluons produced in
proton-proton collisions, we derive the invariant charged-particle yield
dN/dyd^2pT in heavy-ion collisions. Multiple scattering of partons in the other
nucleus leads to pT broadening, which depends on the centrality of the
collision. The resulting change of the LCP parameters determines the
distributions of charged particles. The charged-particle multiplicity dN/deta
at eta=0 normalized to the number of participating nucleons has a universal
centrality dependence, common to RHIC and LHC. This universal increase is of
geometrical origin. Such a universality can be broken by the energy dependent
coherence effect, shadowing and mutual boosting of the saturation scales.
However, we found these effects to essentially compensate each other, leaving
the centrality dependence of multiplicity approximately universal.
