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Elastic electromagnetic form factors of vector mesons

2019; American Physical Society; Volume: 100; Issue: 11 Linguagem: Inglês

10.1103/physrevd.100.114038

2470-0037

Yin-Zhen Xu, Daniele Binosi, Zhu-Fang Cui, B.-L. Li, Craig D. Roberts, Shu-Sheng Xu, Hong-Shi Zong,

Black Holes and Theoretical Physics

A symmetry-preserving approach to the two valence-body continuum bound-state problem is used to calculate the elastic electromagnetic form factors of the $\ensuremath{\rho}$-meson and subsequently to study the evolution of vector-meson form factors with current-quark mass. To facilitate a range of additional comparisons, ${K}^{*}$ form factors are also computed. The analysis reveals that vector mesons are larger than pseudoscalar mesons; composite vector mesons are nonspherical, with magnetic and quadrupole moments that deviate $\ensuremath{\sim}30%$ from point-particle values; in many ways, vector-meson properties are as much influenced by emergent mass as those of pseudoscalars; and vector-meson electric form factors possess a zero at spacelike momentum transfer. Qualitative similarities between the electric form factors of the $\ensuremath{\rho}$ and the proton, ${G}_{E}^{p}$, are used to argue that the character of emergent mass in the Standard Model can force a zero in ${G}_{E}^{p}$. Moreover, the existence of a zero in vector-meson electric form factors entails that a single-pole vector-meson dominance model can only be of limited use in estimating properties of off-shell vector mesons, providing poor guidance for systems in which the Higgs mechanism of mass generation is dominant.