Phys. Rev. Lett. 95, 172503 (2005) [4 pages]Δ Resonance Contribution to Two-Photon Exchange in Electron-Proton ScatteringReceived 9 June 2005; revised 11 October 2005; published 20 October 2005 We calculate the effects on the elastic electron-proton scattering cross section of the two-photon exchange contribution with an intermediate Δ resonance. The Δ two-photon exchange contribution is found to be smaller in magnitude than the previously evaluated nucleon contribution, with an opposite sign at backward scattering angles. The sum of the nucleon and Δ two-photon exchange corrections has an angular dependence compatible with both the polarization-transfer and the Rosenbluth methods of measuring the nucleon electromagnetic form factors. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.95.172503
DOI:
10.1103/PhysRevLett.95.172503
PACS:
25.30.Bf, 12.20.Ds, 13.40.Gp, 14.20.Gk
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