Thresholds of ultraperipheral processes

Abstract: Threshold behavior of the cross sections of ultraperipheral nuclear interactions is studied. Production of $e<sup>+e<sup>-$ and $\mu ^+\mu <sup>-$ pairs as well as $\pi <sup>0$ 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.