Forward dijet production at the LHC within an impact parameter dependent TMD approach

TL;DR

This paper develops a new impact parameter dependent ITMD model to study gluon saturation signatures in forward di-jet production at the LHC, revealing weaker nuclear effects than naive expectations.

Contribution

Introduces an impact parameter dependent ITMD framework for forward di-jet production, incorporating nuclear geometry fluctuations to better understand gluon saturation effects.

Findings

Nuclear saturation scale enhancement is weaker than naive scaling predicts.

Model accounts for event-by-event nuclear geometry fluctuations.

Phenomenological analysis for $p-Pb$, $p-Xe$, and $p-O$ collisions at the LHC.

Abstract

We investigate possible signatures of gluon saturation using forward $p+A \to j+j+X$ di-jet production processes at the Large Hadron Collider. In the forward rapidity region, this is a highly asymmetric process where partons with large longitudinal momentum fraction \(x\) in the dilute projectile are used as a probe to resolve the small \(x\) partonic content of the dense target. Such dilute-dense processes can be described in the factorization framework of Improved Transverse Momentum Distributions (ITMDs). We present a new model for ITMDs where we explicitly introduce the impact parameter (\(b\)) dependence in the ITMDs, to properly account for the nuclear enhancement of gluon saturation effects, and discuss the phenomenological consequences for $p-Pb$, $p-Xe$ and $p-O$ collisions at the LHC. While the case of $p-p$ and $e-p$ collisions is used to fix the model parameters, we find that, on average, the nuclear enhancement of the saturation scale is noticeably weaker than expected from naive scaling with a simple dependence on the atomic number. Since our model explicitly accounts for event-by-event fluctuations of the nuclear geometry, it can also be applied to study forward central correlations in $p-A$ collisions.