Two-photon exchange contributions to elastic ep scattering in the non-local field formalism |
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Authors: | P Jain SD Joglekar S Mitra |
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Institution: | (1) Department of Physics, IIT Kanpur, Kanpur, 208016, India |
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Abstract: | We construct a non-local gauge-invariant Lagrangian to model the electromagnetic interaction of the proton. The Lagrangian
includes all allowed operators with dimension up to five. We compute the two-photon exchange contribution to elastic electron–proton
scattering using this effective non-local Lagrangian. The one-loop calculation in this model includes the standard box and
cross box diagram with the standard on-shell form of the hadron electromagnetic vertices. Besides this we find an extra contribution,
which depends on an unknown constant. We use experimentally extracted form factors for our calculation. We find that the correction
to the reduced cross section is slightly non-linear as a function of the photon longitudinal polarization ε. The non-linearity
seen is within the experimental error bars of the Rosenbluth data. The final result completely explains the difference between
the form factor ratio GE/GM extracted by Rosenbluth separation technique at SLAC and polarization transfer technique at JLAB. |
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