  The energy dependence of charged-hadron production in proton-proton
collisions at RHIC and LHC energies is investigated in a
nonequilibrium-statistical relativistic diffusion model (RDM) with three
sources for particle production. Calculated charged-hadron pseudorapidity
distributions for pp at RHIC energies of sqrt(s) = 0.2 and 0.41 TeV, and at LHC
energies of 0.9, 2.36 and 7 TeV are optimized with respect to the available
data. Predictions for 14 TeV are made. The central source arising from
gluon-gluon collisions becomes the major origin of particle production at LHC
energies. The midrapidity dip is essentially determined by the interplay of the
three sources.
