Nucleon elastic form factors at accessible large spacelike momenta

Abstract

A Poincaré-covariant quark þ diquark Faddeev equation, augmented by a statistical implementation of the Schlessinger point method for the interpolation and extrapolation of smooth functions, is used to compute nucleon elastic form factors on 0 ≤ Q2 ≤ 18m2 N (mN is the nucleon mass) and elucidate their role as probes of emergent hadronic mass in the Standard Model. The calculations expose features of the form factors that can be tested in new generation experiments at existing facilities, e.g., a zero in Gp E=Gp M, a maximum in Gn E=Gn M, and a zero in the proton’s d-quark Dirac form factor, Fd 1. Additionally, examination of the associated light-front-transverse number and anomalous magnetization densities reveals inter alia: a marked excess of valence u quarks in the neighborhood of the proton’s center of transverse momentum, and that the valence d quark is markedly more active magnetically than either of the valence u quarks. The calculations and analysis also reveal other aspects of nucleon structure that could be tested with a high-luminosity accelerator capable of delivering higher beam energies than are currently available.