Bounds on transverse momentum dependent distribution and fragmentation functions

TL;DR

Bounds on the distribution and fragmentation functions that appear at leading order in deep inelastic one-particle inclusive leptoproduction or in Drell-Yan processes are given and are important guidance in estimating the magnitude of the azimuthal and spin asymmetries in these processes.

Abstract

We give bounds on the distribution and fragmentation functions that appear at leading order in deep inelastic 1-particle inclusive leptoproduction or in Drell-Yan processes. These bounds simply follow from positivity of the defining matrix elements and are an important guidance in estimating the magnitude of the azimuthal and spin asymmetries in these processes.

Figures (3)

• Figure 1: Matrix element for distribution functions.
• Figure 2: Matrix element for fragmentation functions.
• Figure 3: Allowed region (shaded) for $\alpha$ and $\beta$ depending on $\gamma$ and $\delta$.