Title :

"Wigner Distributions and Quark Orbital Angular Momentum"

Barbara Pasquini


Abstract :

We discuss the  Wigner functions of the nucleon  which provide multidimensional 
images of the quark distributions in phase space. They depend on both the 
transverse position and the three-momentum of the quark relative to the nucleon, 
and therefore combine in a single picture all the information contained in the 
generalized parton distributions and the transverse-momentum dependent parton 
distributions. We consider a few example of Wigner functions within light-cone 
quark models, discussing the role of the quark orbital angular momentum in 
shaping the nucleon and its correlations with the quark and nucleon polarizations. 
The quark orbital angular momentum is also calculated from the phase-space 
average of the orbital angular momentum operator weighted with the Wigner 
distribution of unpolarized quarks in a longitudinally polarized nucleon. 
The corresponding results obtained within different light-cone quark models 
are compared with alternative definitions of the quark orbital angular momentum, 
as given in terms of generalized parton distributions and transverse-momentum 
dependent parton distributions.