A measurement of two-photon exchange in Super-Rosenbluth separations with positron beams

Abstract

The proton electric and magnetic form factors, $G_E$ and $G_M$, are intrinsically connected to the spatial distribution of charge and magnetization in the proton. For decades, Rosenbluth separation measurements of the angular dependence of elastic e${}^{-}$-p scattering were used to extract $G_E$ and $G_M$. More recently, polarized electron scattering measurements, aiming to improve the precision of $G_E$ extractions, showed significant disagreement with Rosenbluth measurements at large momentum transfers ($Q^2$). This discrepancy is generally attributed to neglected two-photon exchange (TPE) corrections. At larger $Q^2$ values, a new `Super-Rosenbluth' technique was used to improve the precision of the Rosenbluth extraction, allowing for a better quantification of the discrepancy, while comparisons of e${}^{+}$-p and e${}^{-}$-p scattering indicated the presence of TPE corrections, but at $Q^2$ values below where a clear discrepancy is observed. In this work, we demonstrate the significant benefits to combining the Super-Rosenbluth technique with positron beam measurements. This approach provides a greater kinematic reach and is insensitive to some of the key systematic uncertainties in previous positron measurements.

arXiv comment12 pages, 5 figures, accepted for publication in EPJA

References in corpus (40)

• 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
• Two-photon exchange and elastic electron-proton scattering
• How to reconcile the Rosenbluth and the polarization transfer method in the measurement of the proton form factors
• The electric and magnetic form factors of the proton
• Global analysis of proton elastic form factor data with two-photon exchange corrections
• 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
• Partonic calculation of the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer
• Two-photon exchange in elastic electron-nucleon scattering
• Nucleon electromagnetic form factors
• Measurements of electron-proton elastic cross sections for $0.4<Q^2<5.5(GeV/c{)}^2$
• How well do we know the electromagnetic form factors of the proton?
• Review of two-photon exchange in electron scattering
• Final Analysis of Proton Form Factor Ratio Data at ${\mathbf{Q}}^2=4.0$, 4.8 and 5.6 GeV${}^2$
• Proton and neutron electromagnetic form factors and uncertainties
• Nucleon Charge and Magnetization Densities from Sachs Form Factors
• Implications of the discrepancy between proton form factor measurements
• Defining the Proton Radius: a Unified Treatment
• Measurement of the two-photon exchange contribution to the elastic $e^{\pm }p$ scattering cross sections at the VEPP-3 storage ring
• Two-photon exchange in elastic electron-proton scattering
• Towards a resolution of the proton form factor problem: new electron and positron scattering data
• Search for effects beyond the Born approximation in polarization transfer observables in $\vec{e}p$ elastic scattering
• Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment
• Polarization Transfer Observables in Elastic Electron Proton Scattering at $Q^2=$2.5, 5.2, 6.8, and 8.5 GeV${}^2$
• Evidence for two-photon exchange contributions in electron-proton and positron-proton elastic scattering
• Experimental constraints on non-linearities induced by two-photon effects in elastic and inelastic Rosenbluth separations
• Precise determination of low-Q nucleon electromagnetic form factors and their impact on parity-violating e-p elastic scattering
• Measurement of two-photon exchange effect by comparing elastic $e^{\pm }p$ cross sections
• Two-Photon-Exchange Correction to Parity-Violating Elastic Electron-Proton Scattering
• Nucleon Form Factors - A Jefferson Lab Perspective
• $\Delta (1232)$ Resonance Contribution to Two-Photon Exchange in Electron-Proton Scattering Revisited
• Gamma-Z box corrections to weak charges of heavy nuclei in atomic parity violation
• Reanalysis of Rosenbluth measurements of the proton form factors
• Quark-hadron duality constraints on γZ box corrections to parity-violating elastic scattering
• Two-photon exchange corrections to the pion form factor
• Precision Rosenbluth Measurement of the Proton Elastic Electromagnetic Form Factors and Their Ratio at Q^2 = 2.64, 3.20, and 4.10 GeV^2
• Super-Rosenbluth Measurements with Electrons and Positrons

Cited by in corpus (1)

• An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab