Thresholds of ultraperipheral processes

Abstract

Threshold behavior of the cross sections of ultraperipheral nuclear interactions is studied. Production of $e^+e^-$ and $\mu ^+\mu ^-$ pairs as well as $\pi ^0$ and parapositronium is treated. The values of corresponding energy thresholds are presented and the total cross sections of these processes at the newly constructed NICA and FAIR facilities are estimated.