Dr. Wally Meltnichouk

Title: Unraveling the Three-dimensional Structure of the Pion

Abstract: We review recent work by the JAM Collaboration towards extracting the three-dimensional structure of the pion from simultaneous global QCD analysis of collinear parton distribution functions (PDFs) and transverse momentum dependent distributions (TMDs). We explore the constraints on pion PDFs from recent lattice QCD data on reduced Ioffe-time pseudo-distributions and matrix elements of current-current correlators, and assess their impact on the systematic uncertainties. Including for the first time both pT-integrated and pT-dependent pion-nucleus Drell-Yan data from fixed-target experiments, along with leading neutron electroproduction data from HERA, the behavior of the valence quark distribution of the pion at large momentum fraction is found to be ∼(1 − x)^β with β ~ 1. From the transverse momentum dependence of the pion scattering data, we find that the transverse separation of the quark field encoded in TMDs of the pion is smaller than that of the proton, and as a by-product of the analysis we observe evidence for a transverse nuclear EMC effect.