Single-Inclusive Particle Production from $pA$ Collision at Next-to-Leading Order

TL;DR

This paper provides the first fully consistent NLO calculation of single-inclusive forward hadron production in pA collisions within the CGC framework, showing that NLO impact factor corrections suppress the Cronin peak.

Contribution

It introduces a complete NLO calculation including impact factor corrections in the CGC framework for pA collisions, resolving previous contradictions with experimental data.

Findings

NLO impact factor corrections suppress the Cronin peak.

Without impact factor NLO corrections, a significant Cronin peak appears.

Including impact factor corrections aligns theoretical predictions with LHCb results.

Abstract

We present the first fully consistent NLO calculation of the single-inclusive forward hadron production in proton-nucleus (pA) collisions under the color glass condensate (CGC) framework. In the dilute-dense limit, the NLO cross-section can be written as a convolution of the NLO impact factor, NLO parton distribution function (PDF), NLO fragmentation function (FF) and dipole-target scattering amplitude which satisfies the NLO small-$x$ Balitsky-Kovchegov (BK) evolution. We demonstrate that, without the NLO corrections to the impact factor, we obtain a significant Cronin peak when the dipole amplitude satisfies the NLO BK equation. This would contradict the recent LHCb results. However, the Cronin peak becomes suppressed when the NLO correction to the impact factor is included. This is the main result of this work. The dependence on resummation schemes for the NLO BK evolution will also be discussed.