Year: 2003
Type: article
Abstract: Unitary and analytic ten-resonance model of the nucleon electromagnetic (e.m.) structure with canonical normalizations and QCD (up to the logarithmic correction) asymptotics is constructed on the four-sheeted Riemann surface, which provides a superposition of vector–meson pole and continuum contributions in a very natural way. As a result it describes simultaneously all existing experimental space-like and time-like data on the proton e.m. form factors (ff's) and on the neutron e.m. ff's as well. A crucial factor in the latter achievement is the inclusion of a contribution of the fourth excited state of the ρ(770) meson with the parameters m ρ'''' = 2455 ± 53 MeV, Γ ρ'''' = 728 ± 2 MeV and ( f (1) ρ'''' NN / f ρ'''' ) = 0.0549 ± 0.0005, ( f (2) ρ'''' NN / f ρ'''' ) = −0.0103 ± 0.0001. The pronounced effect of the two-pion continuum on the isovector spectral functions demonstrating a strong enhancement of the left wing of the ρ(770) resonance close to two-pion threshold, which was revealed by Höhler and Pietarinen by means of the nucleon ff unitarity condition more than a quarter of the century ago, is predicted by the model automatically. The model gives large values of the f (1,2) ϕ NN coupling constants, thus indicating the violation of the OZI rule. Since in the framework of the considered model isoscalar ff's above their lowest branch point t s 0 = 9 m 2 π are complex functions, the isoscalar spectral function behaviours are predicted as well.
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2093345689