Light-front transverse nucleon charge and magnetization densities

Abstract

Nucleon elastic electromagnetic form factors obtained using both the three-body and quark+fully interacting-diquark pictures of nucleon structure are employed to calculate an array of light-front transverse densities for the proton and neutron and their dressed valence-quark constituents, viz. flavor separations of the proton and neutron results. These two complementary descriptions of nucleon structure deliver mutually compatible predictions, which match expectations based on modern parametrizations of available data, where such are available. Among other things, it is found that transverse-plane valence 𝑢- and 𝑑-quark Dirac radii are practically indistinguishable; but regarding kindred Pauli radii, the 𝑑 quark value is roughly 10% greater than that of the 𝑢-quark. Moreover, magnetically, the valence 𝑑 quark is far more active than the valence 𝑢 quark, probably because it has much greater orbital angular momentum. Both pictures of nucleon structure agree in predicting that, in a polarized nucleon, the transverse-plane charge densities are no longer rotationally invariant. Instead, for a + ^x polarized nucleon, positive charge is displaced in the + ^𝑦 direction, with the opposite effect for negative charge.