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 ≤ Q 2 ≤ 18m 2 N (m N 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 G p E =G p M , a maximum in G n E =G n M , and a zero in the proton's d-quark Dirac form factor, F d 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.

Parton distributions of light quarks and antiquarks in the proton

“…Following Ref. [56], we proceed by using simple algebraic representations for every element, with each form and their relative strengths based on the results of modern analyses [57][58][59][60][61]. Thus freed from cumbersome numerical analysis, this approach brings a clarity that enables quantitative predictions to be made and insights to be drawn.…”

Semileptonic $B_c \to η_c, J/ψ$ transitions

“…All relevant Schwinger functions and, subsequently, the transition form factors are computed as a function of mQ as it is increased from the point r Q :c = 1 to r η c f = 3.17 or r J/ψ f = 2.93. Then, using the statistical Schlessinger point method (SPM), exploited successfully elsewhere [37,39,[58][59][60][61][62][63][64][65], we build mQ -interpolations of all transition form factors, which are then used to extrapolate every measurable feature of the matrix elements to the physical point r b:c = 4.32, Eq. ( 12).…”

Pauli radius of the proton

“…(4), (12). There are many possible contributions to F 2 (Q 2 0), including [7][8][9][10][11][73][74][75][76][77][78]: quark anomalous magnetic moments, quark orbital angular momentum within the proton, meson cloud contributions to one or both, etc. ; and related influences on F 1 (Q 2 0).…”