Two kinds of asymmetry arise from the interference of the Born amplitude
and the box-type amplitude corresponding to two virtual photons exchange, namely
charge-odd and the one spin asymmetries. In case of unpolarized particles the charge-odd
correlation is calculated. It can be measured in combination of electron proton and positron
proton scattering experiments. The forward-backward asymmetry is the corresponding
quantity which can be measured for the crossed processes. In the case of polarized proton
the one-spin asymmetry for annihilation and scattering channels has been calculated.
The additional structure function arising from the interference is explicitly given.
Arguments, based on analyticity, allow to prove that the effect of proton form factors
nearly compensates the contribution of inelastic intermediate states. This justifies the
structureless proton assumption. The uncertainty due to this assumption is discussed. |
