Two-Photon Exchange: Future experimental prospects

Abstract

The proton elastic form factor ratio is accessible in unpolarized Rosenbluth-type experiments as well as experiments which make use of polarization degrees of freedom. The extracted values show a distinct discrepancy, growing with $Q^2$. Three recent experiments tested the proposed explanation, two-photon exchange, by measuring the positron-proton to electron-proton cross section ratio. In the results, a small two-photon exchange effect is visible, significantly different from theoretical calculation. Theory at larger momentum transfer remains untested. This paper discusses the possibilities for future measurements at larger momentum transfer.

7 pages, 4 figures. Contribution to the proceedings of the 11th International Workshop on the Physics of Excited Nucleons (NSTAR 2017)

References in corpus (8)

• 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
• Polarization Transfer in the 4He(e,e'p)3H Reaction at Q^2 = 0.8 and 1.3 (GeV/c)^2
• Towards a resolution of the proton form factor problem: new electron and positron scattering data
• Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment
• Proton G_E/G_M from beam-target asymmetry
• A dispersive approach to two-photon exchange in elastic electron-proton scattering
• Two-photon exchange: myth and history

Cited by in corpus (1)

• Test of streaming and triggered readout schemes for the TPEX Lead Tungstate Calorimeter