Antihydrogen production for specialists

Antihydrogen production for specialists 

      Scheme of e+e- production via the two photon mechanism
in heavy ion collisions: Z1 Z2 -> Z1 Z2 gamma gamma -> Z1 Z2 e+ e-

Two photons in the charge interaction collide and do pair-creation. 

      Scheme of e+e- production and following antihydrogen formation:
pbar Z2 -> pbar gamma gamma Z2 -> pbar e+ e- Z2 -> (pbar e+) e- Z2

If the relative energy of the antiproton and the positron is small enough (<13.7 eV), that is, the positron is produced 'on-shell', both are able to form an antihydrogen atom: 

      pbar Z -> pbar gamma gamma Z -> pbar e+ e- Z -> (pbar e+) e- Z -> antiH e- Z