Ultraperipheral production of lepton pairs (perturbative and nonperturbative effects)

Abstract

Perturbative and nonperturbative terms of the cross-sections of ultraperipheral production of lepton pairs in ion collisions are taken into account. It is shown that production of low-mass [Formula: see text] pairs is strongly enhanced (compared to perturbative estimates) due to the nonperturbative Sommerfeld–Gamow–Sakharov (SGS) factor. Coulomb attraction of the nonrelativistic components of those pairs leads to the finite value of their mass distribution at lowest masses. Their annihilation can result in an increased intensity of 511 keV photons. It can be recorded at the NICA collider and is especially crucial in astrophysical implications regarding the 511 keV line emitted from the Galactic center. The analogous effect can be observed in lepton pairs production at LHC. Energy spectra of lepton pairs created in ultraperipheral nuclear collisions and their transverse momenta are calculated.