Wigner and Husimi Partonic Distributions of the Pion in a Chiral Quark Model

Abstract

Generalized transverse momentum distributions (GTMDs), the Wigner, and the Husimi distributions of quarks in the pion are evaluated in a chiral quark model at the one-loop-level. Analytic expressions are obtained for GTMDs, allowing for a qualitative discussion of their features, whereas the Wigner and the Husimi distribution are obtained with numerical integration of simple formulas. We explain the features of the Wigner distributions, in particular their non-positivity. In our model, the Husimi distributions, which are interpreted as coarse-grained Wigner distributions, are not mathematically positive-definite, but the magnitude of their negative values is tiny and occurs at large transverse momenta and impact parameters. Hence, as expected, coarse-graining leads to better behaved functions from the point of view of the probabilistic interpretation.