Energy spectrum of e+e- pair produced in muon-atom collision

Low-energy part of the spectrum of the e+e- pair, produced in muon-atom collision, when 2>2m, where m and M are electron and muon masses (besides, it is supposed, that P0>>M). Function diagrams for intermediate k0 and z values are given and it essertially simplifies spectrum calculation in these cases together with the presented asymptotics. The maximum of the energy spectrum of the e+e- pair takes place at k0 approximately 12 m, if the energy of the incident muon is sufficiently high