Similarity of Initial States in A+A and p+p Collisions in Constituent Quarks Framework

Abstract

The multiparticle production results from A+A and p(\bar{p})+p collisions have been compared based on the number of nucleon participants and the number of constituent quark (parton) participants. In both normalizations, we observe that the charged particle densities in Au+Au and Cu+Cu collisions are similar for both \sqrt{s_{NN}} = 62.4 and 200 GeV. This implies that in symmetric nucleus-nucleus collisions the charged particle density does not depend on the size of the two colliding nuclei but only on the collision energy. In the nucleon participants framework, the particle density at mid-rapidity as well as in the limiting fragmentation region from A+A collisions are higher than those of p(\bar{p})+p collisions at the same energy. Also the integrated total charged particle in A+A collisions as a function of number nucleon participants is higher than p(\bar{p})+p collisions at the same energy indicating that there is no smooth transition between peripheral A+A and nucleon-nucleon collisions. However, when the comparison is made in the constituent quarks framework, A+A and p(\bar{p})+p collisions exhibit a striking degree of agreement. The observations presented in this paper imply that the number of constituent quark pairs participating in the collision controls the particle production. One may therefore conjecture that the initial states A+A and p+p collisions are similar when the partonic considerations are used in normalization. Another interesting result is that there is an overall factorization of dN/dηshapes as a function of collision centrality between Au+Au and Cu+Cu collisions at the same energy, \sqrt{s_{NN}} = 200 GeV.