Pion TMDs in light-front constituent approach, and Boer-Mulders effect in the pion-induced Drell-Yan process

TL;DR

This paper models the pion's transverse-momentum dependent parton distributions using a light-front constituent approach, compares results with other models, and successfully describes the Boer-Mulders effect in pion-induced Drell-Yan processes.

Contribution

It introduces a light-front constituent model for pion TMDs, compares with other models, and applies it to describe the Boer-Mulders effect in Drell-Yan scattering.

Findings

Model results agree with experimental data after evolution.

The Boer-Mulders function explains the violation of the Lam-Tung relation.

Good agreement with pion valence PDFs from parameterizations.

Abstract

At leading twist the transverse-momentum dependent parton distributions of the pion consist of two functions, the unpolarized $f_{1,\pi}(x,\boldsymbol k^{\, 2}_\perp)$ and the Boer-Mulders function $h_{1,\pi}^{\perp}(x,\boldsymbol k^{\, 2}_\perp)$. We study both functions within a light-front constituent model of the pion, comparing the results with different pion models and the corresponding nucleon distributions from a light-front constituent model. After evolution from the model scale to the relevant experimental scales, the results for the collinear pion valence parton distribution function $f_{1,\pi}(x)$ are in very good agreement with available parameterizations. Using the light-front constituent model results for the Boer-Mulders functions of the pion and nucleon, we calculate the coefficient $\nu$ in the angular distribution of Drell-Yan dileptons produced in pion-nucleus scattering, which is responsible for the violation of the Lam-Tung relation. We find a good agreement with data, and carefully discuss the range of applicability of our approach.