Generalized sachs form factors and the possibility of their measurement in processes without and with proton spin flip

The differential cross section for elastic electron-proton scattering has been calculated taking into account the two-photon exchange within the phenomenological description of the electromagnetic electron-proton interactions. The calculation is based on the consistent evaluation of the matrix elements of the proton current in a diagonal spin basis, which makes it possible to naturally obtain expressions for the generalized Sachs form factors. A new method has been proposed to independently measure these form factors in the elastic $e\vec{p} \to e\vec{p}$ process in the case where the initial proton at rest is fully polarized along the direction of the motion of the final proton.