High-energy electroproduction in the atomic field
Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, prosp. akad. Lavrenteva 11, Novosibirsk, 630090, Russian Federation
We discuss the most recent results in studying high-energy electroproduction in the atomic field. Production of the $\text e^+e^-$ pair by the relativistic electron, relativistic muon or light nucleus and production of the $\mu ^+\mu ^-$ pair by the relativistic electron are reviewed. We focus on an accurate account of the interaction of the incoming particle and produced pair with the atomic field (Coulomb corrections). Interaction of the particle that produces the virtual photon with the atomic field is shown in all the considered cases to significantly change the process cross section differential over that particle's momentum, this conclusion being in contrast to the generally accepted opinion. However, the process cross section integrated over that momentum proves to be only weakly affected by the interaction. Production of pairs in an unbound or bound state (positronium, muonium, and dimuonium) is also discussed.