Probing parton saturation with forward $Z^0$-boson production at small transverse momentum in p+p and p+A collisions

TL;DR

This paper investigates forward Z^0-boson production at small transverse momentum in proton-proton and proton-nucleus collisions, employing both collinear and dilute-dense frameworks with Sudakov resummation, aiming to identify saturation effects.

Contribution

It introduces a comprehensive comparison of the collinear and dilute-dense frameworks with Sudakov resummation for forward Z^0 production, highlighting potential saturation signals in nuclear collisions.

Findings

Sudakov resummation is crucial for accurate transverse momentum distribution.

Predictions show differences in nuclear modification factors indicating saturation effects.

Comparison with different nuclear PDFs reveals sensitivity to saturation phenomena.

Abstract

We calculate and compare the differential cross sections for forward $Z^0$-boson production at small transverse momentum, in proton-proton and proton-nucleus collisions, using both the collinear and dilute-dense factorization frameworks. In both cases, we implement a Sudakov resummation of the large logarithms generated by soft-gluon emissions, which is essential in order to describe the transverse momentum distribution of forward $Z^0$ bosons measured at the Tevatron and the LHC. We further compute the nuclear modification factor in the dilute-dense framework, hoping to single out signals of saturation effects at small values of $x$. Our predictions are compared with those obtained in the collinear factorization framework, using two different nuclear parton distribution functions.