Jet Azimuthal Correlations and Parton Saturation in the Color Glass Condensate

Abstract

We consider the influence of parton saturation in the Color Glass Condensate on the back-to-back azimuthal correlations of high $p_T$ hadrons in $pA$ (or $dA$) collisions. When both near--side and away--side hadrons are detected at mid-rapidity at RHIC energy, the effects of parton saturation are constrained to transverse momenta below the saturation scale $p_T \leq Q_s$; in this case the back-to-back correlations do not disappear but exhibit broadening. However when near-side and away-side hadrons are separated by several units of rapidity, quantum evolution effects lead to the depletion of back-to-back correlations as a function of rapidity interval between the detected hadrons (at fixed $p_T$). This applies to both $pp$ and $pA$ (or $dA$) collisions; however, due to the initial conditions provided by the Color Glass Condensate, the depletion of the back-to-back correlations is significantly stronger in the $pA$ case. An experimental study of this effect would thus help to clarify the origin of the high $p_T$ hadron suppression at forward rapidities observed recently at RHIC.

Figures (13)

• Figure 1: Back-to-back correlations of produced jets in the perturbative phase based on the QCD factorization.
• Figure 2: Two mechanisms of double inclusive production.
• Figure 3: Double inclusive cross section for two correlated jet production in the perturbative phase of QCD (Fig. \ref{['cor2']}-a) and single inclusive cross section for a single jet production (Fig. \ref{['cor2']}-b).
• Figure 4: The Mueller diagram for the production of two gluon jets from different parton showers.
• Figure 5: Fig. \ref{['cor1ps']}-a : Two gluon jet production in one parton shower normalized in a such way that the integral over azimuthal angle is equal to 1. The upper curve corresponds to proton-proton interaction, the middle one describes the deuteron-gold interaction while the third curve is related to gold-gold interaction. The calculation is performed for two jets with $p_1 = 4\,GeV$ and $p_2 = 2\,GeV$ which corresponds to STAR experiment measurements STAR. Fig. \ref{['cor1ps']}-b: Same as in Fig. \ref{['cor1ps']}-a, but for the sum of one and two parton showers.