Polarization Observables in A(d,p)A(d,p) Breakup and Quark Degrees of Freedom in the Deuteron

The differential cross section, the tensor analyzing power, $T_{20}$, and the polarization transfer, $\kappa_0$, in $^{12}C(d,p)$ breakup at relativistic energy are calculated within a model which incorporates multiple scattering and Pauli principle at quark level. It is shown that the rescattering and quark exchange affect drastically the polarization observables for kinematical region corresponding to high internal momentum in the deuteron.Comment: 12 pages, Latex and 4 PostScript figure

Two-photon exchange at low Q^2

We study two-photon exchange for elastic electron-proton scattering at low Q^2. Compact approximate formulae for the amplitudes are obtained. Numerical calculations are done for Q^2 < 0.1 GeV^2 with several realistic form factor parameterizations, yielding similar results. They indicate that the corrections to magnetic form factor can visibly affect cross-section and proton radii. For low-Q^2 electron-neutron scattering two-photon exchange corrections are shown to be negligibly small.Comment: 5 pages, 4 figure

Two-photon exchange amplitudes for the elastic epep scattering at Q^2=2.5 GeV^2 from the experimental data

We extract two-photon exchange amplitudes for the elastic electron-proton scattering at Q^2=2.5 GeV^2 from the unpolarized cross-section and recent polarization transfer measurements. There are three independent amplitudes, but only one of them, \delta G_M, can be determined with a reasonable accuracy(about 10%). The result is in good agreement with theoretical predictions. Rough estimates for two other amplitudes are obtained.Comment: 3 pages, 3 figure