# Difficulties in the description of Drell-Yan processes at moderate invariant mass and high transverse momentum

## TL;DR

This paper investigates the challenges in accurately describing Drell-Yan processes at moderate invariant mass and high transverse momentum, highlighting discrepancies between collinear predictions and experimental data.

## Contribution

It critically assesses the limitations of standard collinear factorization in predicting high-q_T Drell-Yan cross sections and discusses potential effects to improve the description.

## Key findings

- Collinear predictions are often below experimental data at high q_T.
- Additional perturbative and non-perturbative effects are insufficient to reconcile predictions with data.
- Standard frameworks need refinement for accurate high-q_T Drell-Yan modeling.

## Abstract

We study the Drell-Yan cross section differential with respect to the transverse momentum of the produced lepton pair. We consider data with moderate invariant mass Q of the lepton pair, between 4.5 GeV and 13.5 GeV, and similar (although slightly smaller) values of the transverse momentum q_T. We approach the problem by deriving predictions based on standard collinear factorization, which are expected to be valid toward the high-q_T end of the spectrum and to which any description of the spectrum at lower q_T using transverse-momentum dependent parton distributions ultimately needs to be matched. We find that the collinear framework predicts cross sections that in most cases are significantly below available data at high q_T. We discuss additional perturbative and possible non-perturbative effects that increase the predicted cross section, but not by a sufficient amount.