Meson exchange effects in elastic $ep$ scattering at loop level and the electromagnetic form factors of the proton

Abstract

A new form of two-photon exchange(TPE) effect is studied to explain the discrepancy between unpolarized and polarized experimental data in elastic $ep$ scattering. The mechanism is based on a simple idea that apart from the usual TPE effects from box and crossed-box diagrams, the mesons may also be exchanged in elastic $ep$ scattering by two-photon coupling at loop level. The detailed study shows such contributions to reduced unpolarized cross section (${\sigma }_{un}$) and polarized observables ($P_t,P_l$) at fixed $Q^2$ are only dependent on proton's electromagnetic form factors $G_{E,M}$ and a new unknown universal parameter $g$. After combining this contribution with the usual TPE contributions from box and crossed-box diagrams, the ratio ${\mu }_p{G}_E/G_M$ extracted from the recent precise unpolarized and polarized experimental data can be described consistently.

arXiv comment13 pages, 6 figures

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Cited by in corpus (9)

• $\Delta (1232)$ Resonance Contribution to Two-Photon Exchange in Electron-Proton Scattering Revisited
• Two-photon-exchange effects in the unpolarized $\mu p$ scattering within the hadronic model
• Contribution of σ-meson exchange to elastic lepton-proton scattering
• Meson exchange in lepton-nucleon scattering and proton radius puzzle
• Two photon exchange in elastic electron scattering off hadronic systems
• Lepton mass effects for beam-normal single-spin asymmetry in elastic muon-proton scattering
• Two-photon exchange effects in $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ and time-like pion electromagnetic form factor
• Exact Relations for Two-Photon-Exchange Effect in Elastic $ep$ Scattering by Dispersion Relation and Hadronic Model
• Axial meson contribution to proton form factors