Densities, Parton Distributions, and Measuring the Non-Spherical Shape of the Nucleon

Spin-dependent quark densities, matrix elements of specific density operators in proton states of definite spin-polarization, indicate that the nucleon may harbor an infinite variety of non-spherical shapes. We show that these matrix elements are closely related to specific transverse momentum dependent parton distributions accessible in the angular dependence of the semi-inclusive processes electron plus proton goes to electron plus pion plus anything, and the Drell-Yan reaction proton plus proton goes to a lepton anti-lepton pair plus anything. New measurements or analyses would allow the direct exhibition of the non-spherical nature of the proton.Comment: 7 pages, two figure

Travels With Tony-Nucleon Structure Through Our Ages

Nucleon structure is currently understood from a unified light-front, infinite-momentum-frame framework. The specific examples of the neutron transverse charge distribution and the shape of the proton are discussed here.Comment: 6 pages, no figures, text of a talk presented at the workshop "Achievements and New Directions in Subatomic Physics: Festschrift in Honor of Tony Thomas's 60th Birthday