Using dispersion relations, we derive the complete virtual QED contributions to Bhabha scattering due to vacuum polarization effects. We apply our result to hadronic corrections and to heavy lepton and top quark loop insertions. We give the first complete estimate of their net numerical effects for both small and large angle scattering at typical beam energies of meson factories, the CERN Large...

In this introductory exploration of the title theme, we treat a positron as a light nucleus and work within the quasimolecule approximation to obtain, for the first time, adiabatic potential energy curves for its scattering by the He atom. We then show that different elastic and inelastic processes that contribute to the total scattering cross section can be rationalized in molecular terms as d...

This article is a brief overview of opportunities and challenges in the area of low-energy positron and positronium atomic physics. The ideas presented here come from discussion during the final, summary session of the XIII International Workshop on Low Energy Positron and Positronium Physics, Campinas Brazil, July 2005. 2006 Elsevier B.V. All rights reserved. As is the custom, the final sessio...

The hadronic structure of real and virtual photons can be measured in electron positron scattering processes in which one lepton serves as a source of target photons with virtuality P 2 << Q where Q is the virtuality of the probing photon. The measured ee cross section can then be obtained by a convolution of a flux of target photons with the deep inelastic electron (positron) photon scattering...

In positron emission tomography (PET), photon scattering inside the body causes significant blurring and quantification error in the reconstructed images. To solve this problem we have developed Monte Carlo (MC) based 3D PET reconstruction algorithms implemented on the Graphics Processing Unit (GPU). Our implementation takes multiple Compton scattering into account without any significant addit...

Significant discrepancies have been observed between proton form factors as measured by Rosenbluth separation and polarization transfer techniques. There are indications that this difference may be caused by corrections to the one photon exchange approximation that are not taken into account in standard radiative correction procedures. In this paper, we constrain the two-photon amplitudes by co...

We report the first observation of an azimuthal asymmetry in the hard electroproduction of real photons with respect to the charge of the incoming lepton beam. The asymmetry is attributed to the interference between the Bethe–Heitler process and the deeply–virtual Compton scattering process, which gives access to the latter at the amplitude level. This process appears to be the theoretically cl...