The Ridge from the BFKL evolution and beyond

TL;DR

This paper demonstrates that long-range rapidity correlations from BFKL parton showers lead to azimuthal angle correlations and ridge structures in high-energy collisions, with saturation effects playing a significant role.

Contribution

It reveals that initial-state effects from BFKL evolution and gluon saturation can produce ridge-like correlations, providing a unified explanation for phenomena in proton-proton and nucleus-nucleus collisions.

Findings

Long-range correlations generate azimuthal angle correlations.

Gluon saturation significantly influences these correlations.

Ridge structures emerge from BFKL to saturation transition.

Abstract

We show that the long-range rapidity correlations between the produced charged-hadron pairs from two BFKL parton showers generate considerable azimuthal angle correlations. These correlations have no 1/N_c suppression. The effect of gluon saturation on these correlations are discussed and we show that it is important. We show that a pronounced ridge-like structure emerges by going from the BFKL to the saturation region. We show that the ridge structure at high-energy proton-proton and nucleus-nucleus collisions has the same origin and its main feature can be understood due to initial-state effects. Although the effects of final-state interactions in the latter case can be non-negligible.