Quark participants and global observables

One of the challenges in relativistic heavy ion collisions is to measure and study the large number of particles produced in such reactions. Measurement of particle density and transverse energy density in rapidity is a convenient way to describe particle production in heavy ion collisions. The pseudorapidity density (dN/dη) and transverse energy pseudorapidity density (dET /dη) at mid-rapidity is found to increase with increase in centrality of the reaction at SPS and RHIC energies [1, 2, 3, 4]. This has been claimed to be understood using a simple geometrical picture of collision. At SPS energies, it was found that the particle production scales with the number of participating nucleons (NN−part).