Manifestations of high density QCD in the first RHIC data

Abstract

We derive a simple analytical scaling function which embodies the predictions of high density QCD on the energy, centrality, rapidity, and atomic number dependences of hadron multiplicities in nuclear collisions. Both centrality and rapidity dependences of hadron multiplicity in $Au-Au$ collisions as measured at RHIC at $\sqrt{s}= 130 {GeV}$ are well described in this approach. The centrality and rapidity dependences of hadron multiplicity at $\sqrt{s}= 200 \ {GeV}$ run at RHIC are predicted; the variation of these dependences with energy appear different from other approaches, and can be used as an important test of the ideas based on parton saturation and classical Chromo-Dynamics.

Figures (7)

• Figure 1: Hard probe interacting with the nuclear target resolves the transverse area $\sim 1/Q^2$ ($Q^2$ is the square of the momentum transfer) and, in the target rest frame, the longitudinal distance $\sim 1/(m x)$ ($m$ is the nucleon mass and $x$ -- Bjorken variable).
• Figure 2: The Mueller diagram for the classical gluon radiation.
• Figure 3: Centrality dependence of charged hadron production per participant at different pseudorapidity $\eta$ intervals in $Au-Au$ collisions at $\sqrt{s} = 130$ GeV; the data are from PHOBOS130.
• Figure 4: Pseudo--rapidity dependence of charged hadron production at different cuts on centrality in $Au-Au$ collisions at $\sqrt{s} = 130$ GeV; the data are from PHOBOS130.
• Figure 5: Centrality dependence of charged hadron production per participant at different pseudorapidity $\eta$ intervals in $Au-Au$ collisions at $\sqrt{s} = 200$ GeV.