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.