The LHC can probe small x PDFs; the treatment of the infrared region

TL;DR

This paper improves the theoretical predictions for low-mass Drell-Yan processes at the LHC by reducing scale sensitivity and identifies an inconsistency in the standard NLO infrared treatment, enabling better probing of low-x PDFs.

Contribution

It introduces a method to reduce factorization scale sensitivity in NLO Drell-Yan predictions and highlights a fundamental inconsistency in the conventional NLO infrared treatment.

Findings

Reduced scale sensitivity in low-mass Drell-Yan predictions

Identification of an inconsistency in NLO infrared treatment

Potential for more accurate low-x PDF measurements at the LHC

Abstract

First, we show how to reduce the sensitivity of the NLO predictions of the Drell-Yan production of low-mass, lepton-pairs, at high rapidity, to the choice of factorization scale. In this way, observations of this process at the LHC can make direct measurements of parton distribution functions in the low x domain; x < 10^{-4}. Second, we find an inconsistency in the conventional NLO treatment of the infrared region. We illustrate the problem using the NLO coefficient function of Drell-Yan production.