Speaker
Description
Several works have attempted to understand the pion valence partonic distribution function (PDF), both experimentally and theoretically. Questions remain, especially for the high x region. Using the recently developed Residual Field Model, we calculate the pion valence PDF in the range of 0.1<x<1. Within the model, the pion transitions into valence and residual subsystems described by their respective light-front wave functions. Within the valence subsystem, there are two mechanisms that describe the valence quarks of the pion at different x: the soft contribution and the hard quark-quark short-range component. The parameters of soft LF wave functions are fixed by fitting the calculation to the well-established properties of phenomenological pion PDFs. One such property is the peaking structure of x-weighted valence quark distribution in the pion which occurs at x ~ 0.4, where we expect the soft contribution to dominate. We explore different analytic forms for the valence quark-antiquark light front wave function in which the short distance is described by Coulomb-type interaction while the long-distance part is by a harmonic oscillator-like system which accounts for the confinement. With the parameters of soft quark-anti quark and residual wave functions fixed, we calculate the high x -component by considering the mechanism of hard gluon exchange between valence quarks. This allows us to make predictions on the form of the high-x pion PDF distribution that can be verified in the future measurements of pion PDF at a high x limit.
