Systematics of Global Observables in Cu+Cu and Au+Au Collisions at RHIC Energies

Charged particles produced in Cu+Cu collisions at \sqrt{s_{NN}} = 200 and 62.4 GeV have been measured in the PHOBOS experiment at RHIC. The comparison of the results for Cu+Cu and Au+Au for the most central collisions at the same energy reveals that the particle density per nucleon participant pair and the extended longitudinal scaling behavior are similar in both systems. This implies that for the most central events in symmetric nucleus-nucleus collisions the particle density per nucleon participant pair does not depend on the size of the two colliding nuclei but only on the collision energy. Also the extended longitudinal scaling seems independent of the colliding energy and species for central collisions. In addition, there is an overall factorization of dN/dEta shapes as a function of collision centrality between Au+Au and Cu+Cu collisions at the same energy.Comment: 3 pages, 2 figures. Contributed talk at PANIC '05 conference, Santa Fe, NM, Oct 24-28, 200