Pion nucleus Drell-Yan process and parton transverse momentum in the pion

TL;DR

This paper analyzes unpolarized pion-nucleus Drell-Yan processes using NJL model-based pion distributions and nuclear PDFs, achieving good agreement with data and exploring pion transverse momentum structure.

Contribution

It introduces a NJL model-based approach for pion distributions applied to Drell-Yan processes, with scale fixing via NLO predictions and data comparison.

Findings

Fair agreement with experimental pion-nucleus Drell-Yan data.

Significant evolution effects on transverse momentum distributions.

Low invariant mass region is promising for probing pion transverse structure.

Abstract

We present a thorough analysis of unpolarized Drell-Yan (DY) pair production in pion-nucleus scattering. On the nucleus side, we use nuclear parton distributions along with parametrisations of the nucleon partonic transverse distribution available in the literature. Partonic longitudinal and transverse distributions of the pion are those obtained in a recent calculation in a Nambu-Jona Lasinio (NJL) framework, with Pauli-Villars regularization. The scale of the NJL model is fixed by a comparison between NLO predictions based on NJL evolved pion distributions and rapidity differential DY cross sections data. The resulting distributions are then used to describe, up to next-to-leading logarithmic accuracy, the transverse momentum spectrum of dilepton pairs up to a transverse momentum of 2 GeV. With no additional parameters, fair agreement is found with available pion-nucleus data, confirming the virtues of the NJL description of pion parton structure. We find sizable evolution effects on the shape of the distributions and on the generated average transverse momentum of the dilepton pair. We discuss the possibility of extracting details on pion unpolarized transverse momentum dependent parton distribution from pion nucleus DY data. In this respect, the region of low invariant mass of the lepton pair appears to be favored to discriminate between different descriptions of the non-perturbative pion transverse structure.