  A symmetry-preserving Dyson-Schwinger equation treatment of a vector-vector
contact interaction is used to compute dressed-quark-core contributions to the
nucleon $\sigma$-term and tensor charges. The latter enable one to directly
determine the effect of dressed-quark electric dipole moments (EDMs) on neutron
and proton EDMs. The presence of strong scalar and axial-vector diquark
correlations within ground-state baryons is a prediction of this approach.
These correlations are active participants in all scattering events and thereby
modify the contribution of the singly-represented valence-quark relative to
that of the doubly-represented quark. Regarding the proton $\sigma$-term and
that part of the proton mass which owes to explicit chiral symmetry breaking,
with a realistic $d$-$u$ mass splitting the singly-represented $d$-quark
contributes 37% more than the doubly-represented $u$-quark; and in connection
with the proton's tensor charges, $\delta_T u$, $\delta_T d$, the ratio
$\delta_T d/\delta_T u$ is 18% larger than anticipated from simple quark
models. Of particular note, the size of $\delta_T u$ is a sensitive measure of
the strength of dynamical chiral symmetry breaking; and $\delta_T d$ measures
the amount of axial-vector diquark correlation within the proton, vanishing if
such correlations are absent.
