Centrality dependence of high $p_T$ suppression in Au+Au collisions suggest quark matter formation

Abstract

In a pQCD-based model, we have analyzed the STAR data on the high $p_T$ suppression of charged hadrons, in Au+Au collisions at $\sqrt{s}$=200 GeV. In the jet quenching or the energy loss picture, $p_T$ spectra of charged hadrons as well as the $p_T$ dependence of nuclear modification factor, in all the centrality ranges, are well explained, with nearly a constant relative energy loss, $\Delta E/E=0.56\pm 0.03$. Centrality independence of relative energy loss indicate that the matter produced in central and in peripheral collisions are different, otherwise relative energy loss would have shown strong centrality dependence. Qualitatively, centrality independence of relative energy loss can be understood, if in central Au+Au collisions deconfined matter is produced and the matter remain confined in peripheral collisions.