Rapidity Distributions Of Pions In P Plus P And Pb Plus Pb Collisions At Energies Available At The Cern Super Proton Synchrotron

The centrality dependence of rapidity distributions of pions in Pb+Pb reactions can be understood by imposing local energy-momentum conservation in the longitudinal "fire streaks" of excited matter. With no tuning nor adjustment to the experimental data, the rapidity distribution of pions produced by the fire streak which we obtained from Pb+Pb collisions reproduces the shape of the experimental pion rapidity distribution in p + p interactions, measured by the NA49 Collaboration at the same energy. The observed difference in the absolute normalization of this distribution can be explained by the difference in the overall energy balance, induced by baryon stopping and strangeness enhancement phenomena occurring in heavy ion collisions. We estimate such effects using a collection of Super Proton Synchrotron experimental data on pi(+/-), K-+/-, net p, and n production in p + p and Pb+Pb reactions. Implications of the above findings are discussed.