Search for effects beyond the Born approximation in polarization transfer observables in $\vec{e}p$ elastic scattering

Abstract

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $G_E/G_M$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic $H(\vec{e},e^{\prime }\vec{p})$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2=2.5$ GeV${}^2$, spanning a wide range of the virtual photon polarization parameter, $\epsilon$. From these measured polarization observables, we have obtained separately the ratio $R$, which equals ${\mu }_p{G}_E/G_M$ in the Born approximation, and the longitudinal polarization transfer component $P_{\ell }$, with statistical and systematic uncertainties of $ΔR \approx \pm 0.01 \mbox{(stat)} \pm 0.013 \mbox{(syst)}$ and $ΔP_\ell/P^{Born}_{\ell} \approx \pm 0.006 \mbox{(stat)}\pm 0.01 \mbox{(syst)}$. The ratio $R$ is found to be independent of $\epsilon$ at the 1.5% level, while the $\epsilon$ dependence of $P_{\ell }$ shows an enhancement of $(2.3\pm 0.6)$ relative to the Born approximation at large $\epsilon$.

References in corpus (20)

• The ratio of proton's electric to magnetic form factors measured by polarization transfer
• Measurement of GEp/GMp in ep -> ep to Q2 = 5.6 GeV2
• Nucleon Electromagnetic Form Factors
• Proton elastic form factor ratios to $Q^2$ = 3.5 GeV${}^2$ by polarization transfer
• How to reconcile the Rosenbluth and the polarization transfer method in the measurement of the proton form factors
• Precision Rosenbluth measurement of the proton elastic form factors
• Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2
• Two-photon exchange in elastic electron-nucleon scattering
• Measurements of electron-proton elastic cross sections for $0.4<Q^2<5.5(GeV/c{)}^2$
• The two-photon exchange contribution to elastic electron-nucleon scattering at large momentum transfer
• Nucleon Form Factors in QCD
• Two-Photon Physics in Hadronic Processes
• $\Delta$ resonance contribution to two-photon exchange in electron-proton scattering
• Charged pion form factor between $Q^2$=0.60 and 2.45 GeV${}^2$. I. Measurements of the cross section for the ${}^1$H($e,e^{\prime }{\pi }^{+}$)$n$ reaction
• Evidence for two-photon exchange contributions in electron-proton and positron-proton elastic scattering
• Extraction of two-photon contributions to the proton form factors
• Two-photon exchange in elastic electron-proton scattering : QCD factorization approach
• The structure function method applied to polarized and unpolarized electron-proton scattering: a solution of the G_E(p)/G_M(p) discrepancy
• Model independent radiative corrections in processes of polarized electron-nucleon elastic scattering
• The ratio of $e^{\pm }p$ scattering cross sections predicted from the global fit of elastic $ep$ data

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