ENERGY AND SYSTEM SIZE DEPENDENCE STUDY OF THE PERCOLATION PHASE TRANSITION

Multiparticle production at high energies is described in terms of color strings stretched between the projectile and target. As the string density increases, overlap in the transverse plane leads to cluster formation. At some critical density a macroscopic cluster appears, spanning the entire system. This marks the percolation phase transition. Data from p+p, d+Au and Au+Au collisions at RHIC has been analyzed using the STAR detector to obtain the percolation density parameter, η. The particle p_T spectrum from 200 GeV p+p data is parametrized using a power law. Values of the fit parameters are used in the d+Au and Au+Au analysis. For 200 GeV Au+Au collisions, the value of η is found to lie above the critical percolation threshold, while for other collision systems and energies, it is below the critical value. This supports the idea of string percolation, which at high enough string density is a possible mechanism to explore the hadronic phase transition to a quark-gluon plasma.