Generalized Cahn effect and parton 3D motion in a covariant approach

TL;DR

This paper investigates the Cahn effect and parton transverse momentum distributions using a covariant model, revealing gaps in current understanding and providing new relations and predictions for parton distribution functions.

Contribution

It introduces a new covariant relation for the unpolarized parton distribution function and compares the Cahn effect with other intrinsic motion effects.

Findings

Current understanding of parton transverse momentum is incomplete.

A new covariant relation for $f_{1}^{q}(x, p_T)$ is derived.

Predictions for the distribution function are provided.

Abstract

The Cahn effect and the unintegrated unpolarized parton distribution function $f_{1}^{q}(x,\mathbf{p}_{T})$ are studied in a covariant approach. The Cahn effect is compared with some other effects due to the parton intrinsic motion. The comparison suggests that the present understanding of parton transverse momenta and intrinsic motion in general is still rather incomplete. The new relation for $f_{1}^{q}(x,\mathbf{p}_{T})$ is obtained in the framework of the covariant parton model from which a prediction for this distribution function follows.