Boosted saturation bound in colliding nuclei

TL;DR

This paper investigates how the saturation scale in colliding nuclei is enhanced in pA and AA collisions, deriving bootstrap equations to quantify the boost effect, which is more significant at LHC energies.

Contribution

It introduces a set of bootstrap equations relating saturation scales in colliding nuclei and demonstrates the boosting effect's energy dependence, especially at LHC.

Findings

Boosted saturation scales in AA collisions compared to pA.

Moderate boosting effect at RHIC energies.

Significant boosting effect at LHC energies.

Abstract

Interaction with a nucleus in pA collisions enhances the higher Fock components in the projectile proton. Effectively, this corresponds to an increase of the hard scale of the process by the saturation momentum Q^2 -> Q^2+Q_{sA}^2, which leads to an increased gluon distribution function at small x (but suppressed at x -> 1) compared to that in pp collisions. In the case of AA collisions the gluon distributions of bound nucleons in both nuclei turn out to be enhanced, i.e. to be boosted to higher saturation scales compared to pA collisions. A set of bootstrap equations relating the saturation scales in the colliding nuclei is derived and solved. The boosting effect has a moderate magnitude at the energies of RHIC, but becomes significant at LHC.