2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/200700Spin-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.7 pages, two figuresNuclear TheoryHigh Energy Physics - ExperimentHigh Energy Physics - PhenomenologyNuclear Experimenttext