Thermalization at RHIC

Abstract

Ideal hydroynamics provides an excellent description of all aspects of the single-particle spectra of all hadrons with transverse momenta below about 1.5-2 GeV/c at RHIC. This is shown to require rapid local thermalization at a time scale below 1 fm/c and at energy densities which exceed the critical value for color deconfinement by an order of magnitude. The only known thermalized state at such energy densities is the quark-gluon plasma (QGP). The rapid thermalization indicates that the QGP is a strongly interacting liquid rather than the weakly interacting gas of quarks and gluons that was previously expected.Comment: Erroneous formulation on p.2 corrected. 16 pages, incl. 4 postscript figures. Invited talk presented at HADRON-RANP 2004 (IX Hadron Physics and VII Relativistics Aspects of Nuclear Physics: A Joint Meeting on QCD and QGP), Angra dos Reis, Rio de Janeiro, Brazil, March 28 - April 3, 2004. To appear in AIP Conference Proceedings (M. Bracco, M. Chiapparini, et al., eds.