Related papers: Meson exchange in lepton-nucleon scattering and pr…
Lepton mass effects play a decisive role in description of elastic lepton-proton scattering when the beam's energy is comparable to the mass of the lepton. The future MUSE experiment, which is devised to solve the "Proton Radius Puzzle", is…
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…
We calculate two-photon exchange amplitude for the elastic electron-pion scattering in the dispersion-relation inspired approach, including both elastic and inelastic contributions. The latter was modelled as a sum of \rho and b_1(1235)…
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…
We extend the general formalism of two-photon exchange to elastic lepton-nucleon scattering by accounting for all lepton mass terms. We then perform a numerical estimate of the muon-proton scattering at low momentum transfer in view of the…
We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer $Q^2$. It is shown that the leading two-photon exchange amplitude behaves as $1/Q^4$ relative to the one-photon amplitude, and…
We present the dispersion relation approach based on unitarity and analyticity to evaluate the two-photon exchange contribution to elastic electron-proton scattering. The leading elastic and first inelastic $\pi N$ intermediate state…
We evaluate the two-photon exchange correction to the elastic electron-proton scattering cross section within a dispersive framework. Besides the elastic contribution, we account for all $\pi N$ intermediate state contributions using the…
We calculate two-photon exchange amplitude for the elastic electron-proton scattering in the framework of dispersion relations. The imaginary part of the amplitude is determined by unitarity. Since in the unitarity relation intermediate…
Using the available cross section and polarization data for elastic electron-proton scattering, we provide an extraction of the two-photon exchange amplitudes at a common value of four-momentum transfer, around Q^2 = 2.5 GeV^2. This…
It has been suggested that two-photon exchange corrections could explain the discrepancy between Rosenbluth extractions of the proton form factors and recent polarization transfer measurements. We propose a precise comparison of…
Two-photon exchange contributions to elastic electron-proton scattering cross sections are evaluated in a simple hadronic model including the finite size of the proton. The corrections are found to be small in magnitude, but with a strong…
The effect of the lepton's mass is significantly enhanced when the beam's energy is on the order of the lepton's mass. In the case of electrons, this corresponds to beam momenta on the order of a few MeV and is negligible in higher energy…
The uncertainty in the contribution to the Lamb shift in muonic hydrogen, $\Delta E^{subt}$ arising from proton polarizability effects in the two-photon exchange diagram at large virtual photon momenta is shown large enough to account for…
Systematic differences in the the proton's charge radius, as determined by ordinary atoms and muonic atoms, have caused a resurgence of interest in elastic lepton scattering measurements. The proton's charge radius, defined as the slope of…
We evaluate the two-photon exchange correction to the unpolarized cross section in the elastic muon-proton scattering within dispersion relations. One of the six independent invariant amplitudes requires a subtraction. We fix the…
We consider the role of the two-photon corrections to the small angle $\mu p$ and $ep$ elastic scattering and the expected $\sigma(\mu^- p)/\sigma(\mu^+ p)$ ratio.
Measurements of the ratio of the proton elastic form factors ($\mu_pG_E/G_M$) using Rosenbluth separation and those using polarization-based techniques show a strong discrepancy, which increases as a function of $Q^2$. The contribution of…
We calculate the effects on the elastic electron-proton scattering cross section of the two-photon exchange contribution with an intermediate $\Delta$ resonance. The $\Delta$ two-photon exchange contribution is found to be smaller in…
We present an exact evaluation of the two-photon exchange contribution to the elastic lepton-proton scattering process at low-energies using heavy baryon chiral perturbation theory. The evaluation is performed including next-to-leading…