Realizing vector meson dominance with transverse charge densities

Abstract

The transverse charge density in a fast-moving nucleon is represented as a dispersion integral of the imaginary part of the Dirac form factor in the timelike region (spectral function). At a given transverse distance b the integration effectively extends over energies in a range sqrt{t} ~< 1/b, with exponential suppression of larger values. The transverse charge density at peripheral distances thus acts as a low-pass filter for the spectral function and allows one to select energy regions dominated by specific t-channel states, corresponding to definite exchange mechanisms in the spacelike form factor. We show that distances b ~ 0.5 - 1.5 fm in the isovector density are maximally sensitive to the rho meson region, with only a ~10% contribution from higher-mass states. Soft-pion exchange governed by chiral dynamics becomes relevant only at larger distances. In the isoscalar density higher-mass states beyond the omega are comparatively more important. The dispersion approach suggests that the positive transverse charge density in the neutron at b ~ 1 fm, found previously in a Fourier analysis of spacelike form factor data, could serve as a sensitive test of the the isoscalar strength in the ~1 GeV mass region. In terms of partonic structure, the transverse densities in the vector meson region b ~ 1 fm support an approximate mean-field picture of the motion of valence quarks in the nucleon.

14 pages, 12 figures

References in corpus (9)

• Nucleon Electromagnetic Form Factors
• Dispersion analysis of the nucleon form factors including meson continua
• Flavor decomposition of the elastic nucleon electromagnetic form factors
• Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp
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• Quantifying the nucleon's pion cloud with transverse charge densities
• The neutron negative central charge density: an inclusive-exclusive connection

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• Light-front representation of chiral dynamics with Delta isobar and large-N_c relations
• Exploring Baryon Resonances with Transition Generalized Parton Distributions: Status and Perspectives
• Transverse charge and current densities in the nucleon from dispersively improved chiral effective field theory
• Quantum-mechanical picture of peripheral chiral dynamics
• Kaon transverse charge density from space- and timelike data
• Sea quark transverse momentum distributions and dynamical chiral symmetry breaking
• Transverse charge and magnetization densities in the nucleon's chiral periphery