Lorentz invariance relations between parton distributions and the Wandzura-Wilczek approximation

TL;DR

This paper investigates the Lorentz invariance relations among parton distributions, showing they are approximately valid within a generalized Wandzura-Wilczek approximation, suggesting small violations in practice.

Contribution

It demonstrates that Lorentz invariance relations are not violated in a generalized Wandzura-Wilczek approximation, providing a model-independent analysis.

Findings

Lorentz invariance relations are approximately valid.

Violations of these relations may be numerically small.

The analysis is model-independent.

Abstract

The violation of the so-called Lorentz invariance relations between parton distribution functions is considered in a model independent way. It is shown that these relations are not violated in a generalized Wandzura-Wilczek approximation, indicating that numerically their violation may be small.