Probing Relativistic Spin Effects in the Nucleon by Means of Drell-Yan Processes

TL;DR

This paper investigates relativistic spin effects in the nucleon using Drell-Yan processes, highlighting differences in polarized parton distributions and proposing an observable for future experimental validation at RHIC and HERA--$ar{N}$.

Contribution

It introduces a light-front covariant quark model to analyze relativistic spin effects and defines a specific observable for experimental detection.

Findings

Relativistic spin effects cause significant differences in polarized distributions.

These effects persist at higher Q^2 scales after evolution.

A measurable double-spin asymmetry observable is proposed.

Abstract

Significant differences between transverse and longitudinal polarized parton distributions are found at low energies within a light-front covariant quark model of the nucleon. These differences are due to relativistic spin effects introduced by the Melosh rotations and survive evolution to higher $Q^2$ scales. A specific observable related to double-spin asymmetries in lepton pair production in polarized hadron-hadron collisions is defined. The possibility of assessing the relevance of these relativistic spin effects in future experiments at RHIC and HERA--$\vec{N}$ is discussed.