Colour strings vs. hard pomeron in perturbative QCD
  Average multiplicities and transverse momenta in AA collisions are studied in the soft and hard regions, in fusing string and perturbative QCD scenarios respectively. Striking similarities are found between the predictions of the two approaches. Multiplicities per string and average p_t^2 are found to, respectively, drop and rise with A in a very similar manner, so that their product is nearly a constant. In both approaches total multiplicities grow as A, that is as the number of participants. The high tail of the p_t distribution is found to behave as A^1.1 in the perturbative QCD scenario. 
M.A.Braun and C.Pajares