Theoretical studies of antihydrogen formation in collisions between positronium atoms and antiprotons

The current state of the theoretical methods that are used in calculations of cross sections for the production of antihydrogen in collisions between antiprotons and positronium atoms is reviewed. A broad outline of available methods together with the results of recent computations are presented. The main emphasis is made on the general close-coupling approach that allows any reaction channel to be taken as the initial state of the collision system. In this way, and on account of charge-conjugation invariance, the formation of antihydrogen in collisions between antiprotons and positronium atoms becomes linked to positron-hydrogen scattering and the same computational methods can be applied to either reaction. The review gives references to recent papers on the subject.