QED radiative corrections to elastic electronproton scattering at low energies are discussed. Corrections to the electron line and effects due to vacuum polarization are computed. Higher order effects are estimated for the conditions of the experiment on the electric and magnetic proton form factors by the A1 Collaboration. Calculations are performed within the next-to-leading approximation. The inclusion of the higher order effects can affect the value of the proton charge radius extracted from the experimental data.
The Sommerfeld-Gamow-Sakharov factor is considered for the general case of
arbitrary masses and energies. It is shown that the scalar triangular one-loop
diagram gives the Coulomb singularity in radiative corrections at the
threshold. The singular part of the correction is factorized at the complete
Born cross section regardless of its partial wave decomposition. Different
approaches to generalize the factor are discussed.Comment: 9 pages, 4 figures; references and discussion are extende
Abstract:The Sommerfeld-Gamow-Sakharov factor is considered for the general case of arbitrary masses and energies. It is shown that the scalar triangular one-loop diagram gives the Coulomb singularity in radiative corrections at the threshold. The singular part of the correction is factorized at the complete Born cross section regardless of its partial wave decomposition. Different approaches to generalize the factor are discussed.
Radiative muon and tau lepton decays are described within the model-independent approach with the help of generalized Michel parameters. The exact dependence on charged lepton masses is taken into account. The results are relevant for modern and future experiments on muon and tau lepton decays.
Forward–backward (charge) asymmetry in the processes of [Formula: see text] annihilation into a pair of charged pseudoscalar mesons is recalculated in the one-loop approximation. The exact dependence on the meson masses is taken into account. Results known in the literature are partially corrected. The bulk of the charge asymmetry appears due to double-photon exchange in [Formula: see text] channel. Experimental studies of the asymmetry can be used to verify the point-like approximation used in calculation of radiative corrections due to emission of photons by pions or kaons.
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