5,146 research outputs found
Two-photon exchange in elastic electron-proton scattering : QCD factorization approach
We estimate the two-photon exchange contribution to elastic electron-proton
scattering at large momentum transfer . It is shown that the leading
two-photon exchange amplitude behaves as relative to the one-photon
amplitude, and can be expressed in a model independent way in terms of the
leading twist nucleon distribution amplitudes. Using several models for the
nucleon distribution amplitudes, we provide estimates for existing data and for
ongoing experiments.Comment: 4 pages, 4 figure
Axial anomaly and the delta_{LT} puzzle
The axial anomaly contribution to generalized longitudinal-transverse
polarizability is calculated within Regge approach. It is
shown that the contribution from the exchange of the Regge
trajectory is nontrivial and might have the key role to explain the large
difference between the predictions of chiral perturbation theory and the
experimental data for the neutron . We also present the
prediction for the proton , which will be measured at the
Thomas Jefferson National Accelerator Facility in near future.Comment: 5 pages, 3 figures, REVTeX, to be published in Phys. Rev.
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