Spectral content of isoscalar nucleon form factors

Abstract

The nucleon strange vector and isoscalar electromagnetic form factors are studied using a spectral decomposition. The KK contribution to the electric and magnetic radii as well as the magnetic moment is evaluated to all orders in the strong interaction using an analytic continuation of experimental KN scattering amplitudes and bounds from unitarity. The relationship between non-resonant and resonant KK contributions to the form factors is demonstrated, and values for the vector and tensor φNN couplings are derived. The KK spectral functions are used to evaluate the credibility of model calculations for the strange quark vector current form factors.

Peripheral transverse densities of the baryon octet from chiral effective field theory and dispersion analysis

“…We emphasize that this identification is based on the assumptions of vector dominance and ideal mixing (see Appendix C) and can only provide a rough estimate of the strange-nonstrange separation of the isoscalar current (for a discussion of the uncertainties of the flavor separation of the isoscalar nucleon form factors, see Refs. [74,75,76]). The results presented in the following are intended only to illustrate the basic features of the spatial dependence of the flavor densities in the peripheral region.…”

“…Treatment of the φ as a resonance in the two-kaon channel, along the lines of the ρ in the two-pion channel, is impractical because of the mixing with the three-pion and other hadronic channels; see Refs. [74,75] for a discussion.…”

Nucleon anapole moment and parity-violatingepscattering

“…(39)(40) and (48-49), to obtain a numerical estimate for the R T =0,1 A | anapole . To do so, we use the global fit value for the weak mixing angle in the on-shell scheme, sin 2 θ W = 0.2230 [3], g A = 1.267 ± 0.004 [3], f ρ = 5.26 [33], f ω = 17, f φ = 13 [34], α = F/(D + F ) = 0.36, µ = Λ χ . We express all the PV coupling constants in units of g π = 3.8 × 10 −8 as is traditionally done [29,16].…”

Measurement of the strange quark contribution to the vector structure of the proton

“…In this case, F~s)(O) = 0, as the nucleon carries no net strangeness, and the unsubtracted dispersion relation is used for Fd") (t) since one would like to predict the value of the magnetic form factor at are often called the spectral functions, as they imply dynamical contributions to the form factors from the intermediate states . The general dispersion relation includes all possible on-shell interme-diate states, unlike VMD, which only includes a few off-shell vector meson resonance [129]. For the isoscalar and strangeness form factors, the allowable continuum includes 37r, 57r, KK, NN, etc.…”