No abstract

We discuss two special limiting forms of QCD matter which may be produced at RHIC. We conclude from the available empirical evidence that an equilibrated, but strongly coupled Quark Gluon Plasma has been made in such collisions. We also discuss the growing body of evidence that its source is a Color Glass Condensate.

A systematic expansion of the induced inclusive gluon radiation associated with jet production in a dense QCD plasma is derived using a reaction operator formalism. Analytic expressions for the transverse momentum and light-cone momentum distributions are derived to all orders in powers of the gluon opacity of the medium, N σg/A = L/λg. The reaction operator approach also leads to a simple algebraic proof of the "color triviality" of single inclusive distributions and to a solvable set of recursion relations. The analytic solution generalizes previous continuum solutions (BDMPS) for applications to mesoscopic QCD plasmas. The solution is furthermore not restricted to uncorrelated geometries and allows for evolving screening scales as well as the inclusion of finite kinematic constraints. The later is particularly important because below LHC energies the kinematic constraints significantly decrease the non-abelian energy loss. Our solution for the inclusive distribution also generalizes the finite order exclusive (tagged) distribution case studied previously (GLV1). The form of the analytic solution is well suited for numerical implementation in Monte Carlo event generators to enable more accurate calculations of jet quenching in ultra-relativistic nuclear collisions. Numerical results illustrating the constributions of the first three orders in opacity are compared to the "self-quenching" hard radiation intensity. A surprising result is that the induced gluon radiation intensity is dominated by the (quadratic in L) first order opacity contribution for realistic geometries and jet energies in nuclear collisions.

The sensitivity of moderate /?r^8 GeV/c singles inclusive spectra in nuclear collisions to gluon shadowing and jet quenching is estimated using the HIJING Monte Carlo model. We show how the systematic study of the nuclear dependence of those spectra in p + A can be used to determine the magnitude of gluon shadowing and how the enhanced suppression in A +A would provide information on the energy loss mechanisms in dense partonic matter.