On the use of a running coupling in the calculation of forward hadron production at next-to-leading order

TL;DR

This paper investigates discrepancies in forward hadron production calculations at next-to-leading order, identifies Fourier transform artifacts as the cause, and proposes a new coordinate space prescription to resolve the issue.

Contribution

It introduces a new coordinate space prescription for the running coupling that eliminates artifacts caused by Fourier transforms in NLO calculations.

Findings

The Fourier transform causes artificial large discrepancies in results.

A new coordinate space prescription removes these artifacts.

The proposed method yields more consistent NLO predictions.

Abstract

We study a puzzle raised recently regarding the running coupling prescription used in the calculation of forward particle production in proton-nucleus collisions at next-to-leading order: using a coordinate space prescription which is consistent with the one used in the high energy evolution of the target leads to results which can be two orders of magnitude larger than the ones obtained with a momentum space prescription. We show that this is an artefact of the Fourier transform involved when passing between coordinate and momentum space and propose a new coordinate space prescription which avoids this problem.