Contact-interaction Faddeev equation and,inter alia, proton tensor charges

A confining, symmetry-preserving, Dyson-Schwinger equation treatment of a vector vector contact interaction is used to formulate Faddeev equations for the nucleon and Δ-baryon in which the kernel involves dynamical dressed-quark exchange and whose solutions therefore provide momentum-dependent Faddeev amplitudes. These solutions are compared with those obtained in the static approximation and with a QCD-kindred formulation of the Faddeev kernel. They are also used to compute a range of nucleon properties, amongst them: the proton's σ-term; the large Bjorken-x values of separate ratios of unpolarized and longitudinally polarized valence u- and d-quark parton distribution functions; and the proton's tensor charges, which enable one to directly determine the effect of dressed-quark electric dipole moments (EDMs) on neutron and proton EDMs.