Elastic meson form factors with modified vector resonance propagators

Abstract

Sakurai's ${\mathrm{SU}}_{F}(3)$ universality symmetry is employed to provide a unified description of pseudoscalar meson nonet elastic form factors calculated using a modified vector meson dominance (VMD) formalism. We incorporate excited resonances with modified propagators derived from analyticity and elastic unitarity, employing a single channel $N/D$ approximation to model nonresonant meson exchange contributions. Existing spacelike and timelike data for ${\ensuremath{\pi}}^{+},$ ${K}^{+}$, and ${K}^{0}$ mesons indicate that finite width corrections to the $\ensuremath{\rho}$ propagator and couplings are essential for a precise theoretical description in the VMD framework. Our analysis verifies that existing data cannot rule out the possible existence of two unconfirmed resonances (one narrow isoscalar and one broad isovector) just below and above the $p\overline{p}$ threshold previously suggested to explain the anomalous features observed in timelike ${G}_{M}^{p}$ LEAR and ${G}_{E}^{n}$ FENICE data.