Evolution of particle density in high-energy pp collisions

We study the evolution of the particle density, dn/d\eta at fixed \eta with the beam rapidity Y in the framework of string percolation model. Our main results are: (i) The width of the "plateau" increases proportionally to Y, (ii) limiting fragmentation is violated, and (iii) the particle density, reduces to a step function.Comment: 8 pages, 2 figures, to appear in Nuclear Physics A. Minor changes are don

Absorption and J/psi Suppression in Heavy Ion Collisions

We discuss the J/psi suppression in the framework of multiple collision models. From the analysis of the Pb-Pb NA50 data we conclude that the strength of the absorption has increased, but we find no clear evidence for the formation of the quark-gluon plasma.Comment: 8 pages, 4 figure

String Percolation and the Glasma

We compare string percolation phenomenology to Glasma results on particle rapidity densities, effective string or flux tube intrinsic correlations, the ridge phenomena and long range forward-backward correlations. Effective strings may be a tool to extend the Glasma to the low density QCD regime. A good example is given by the minimum of the negative binomial distribution parameter k expected to occur at low energy/centrality.Comment: Submitted to Phys. Lett

Energy conservation and scaling violations in particle production

We use a simple Colour Glass Condensate/String Percolation Model argument to show the existence, due to energy conservation, of bounds to the violation of Feynman scaling and limiting fragmentation.Comment: 5 pages, 1 figure. Final versio

Density saturation and the decrease of the normalised width of the multiplicity distribution in high energy pp collisions

It is experimentally observed that the width of the KNO multiplicity distribution --or the negative binomial parameter 1/k-- for pp collisions, in the energy region 10 to 1800 GeV, is an increasing function of the energy. We argue that in models with parton or string saturation such trend will necessary change: at some energy the distribution will start to become narrower. In the framework of percolating strings, we have estimated the change to occur at an energy of the order of 5--10 TeV.Comment: 10 pages, 4 figures, uses elsart and amsmath; comparison with some other models was added; version accepted by PL

Cumulative particle production as a rare event

The generalization of the Glauber formula for cumulative production events is derived. On its basis the multiplicity distribution in such events is related to the one in the minimum bias events. As compared to the rare events of type $C$, the formula involves a shift in the arguments determined by the multiplicity from a collision with a cluster of several nucleons.Comment: 11 pages, LaTe

Percolation approach to phase transitions in high energy nuclear collisions

We study continuum percolation in nuclear collisions for the realistic case in which the nuclear matter distribution is not uniform over the collision volume, and show that the percolation threshold is increased compared to the standard, uniform situation. In terms of quark-gluon plasma formation this means that the phase transition threshold is pushed to higher energies.Comment: 7 pages, 4 figures (PS), LaTeX2e using fontenc, amsmath, epsfi

Particle rapidity density and collective phenomena in heavy ion collisions

We analyse recent results on charged particle pseudo-rapidity densities from RHIC in the framework of the Dual String Model, in particular when including string fusion. The model, in a simple way, agrees with all the existing data and is consistent with the presence of the percolation transition to the Quark-Gluon Plasma already at the CERN-SPS. It leads to strict saturation of the particle (pseudo-)rapidity density, normalised to the number of participant nucleons, as that number increases. A comparison with recent WA98 data is presented.Comment: 6 pages, 3 ps figures, Latex2e with amsmath. To appear in the Proceedings of the XXX International Symposium on Multiparticle Dynamics (Lake Balaton, October 2000