Physics of the first 0.3 fm/c at RHIC

Abstract

We have studied multiple gluon production at the first impact of pp and AA collisions, using large order tree diagrams. We have found that this gluon production mechanism at RHIC is more important comparing to simpler processes considered before. Predictions depend strongly on perturbative cutoff, which we evaluate in a self-consistent way. The estimated entropy production at first impact at RHIC Au+Au collisions is comparable or even larger than usual extrapolations. In the LHC case, earlier estimates are but a first term of divergent series: presumably, non-perturbative theory has to be developed here.