Hard exclusive two photon processes in QCD

Victor L. Chernyak, Simon I. Eidelman

This is a short review of some hard two-photon processes: $\\ a) \,\,γγ\to {\overline P}_1 P_2,\,\, {\overline P}_1 P_2= \{π^+π^-, K^+ K^-, K_S K_S, π^oπ^o, π^oη\}\,, \\ b) \,\,γγ\…