CGC-induced longitudinal ridge in p-Pb collisions

Abstract

Within the Color Glass Condensate (CGC) effective field theory, we investigate the long-range rapidity correlations in proton-lead (p-Pb) collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. A distinctive correlation rebound is observed, where the correlation bounces after reaching a minimum at large rapidity gaps ($|\Delta \eta|>2$). The rebound means a strong correlation appears at large rapidity gap. Studying the rebound structures can thus illuminate the formation of the ridge. We find that the rebound is most obvious when the transverse momenta of two measured particles are around 2 $\mathrm{GeV/c}$, and it moves to larger rapidity gaps at higher collision energies. Beyond that, the rapidity correlations in p-Pb collisions show asymmetry when the transverse momenta of two particles differ. The asymmetry, a unique signature of the asymmetric collisions, vanishes when the transverse momenta of two particles coincide. These findings provide direct insight into gluon saturation and quantum evolution.