A quark model calculation of γγ→ππ including final-state interactions

Abstract

A quark model calculation of the processes γγ→π+π- and γγ→π0π0 is performed. At tree level, only charged pions couple to the initial state photons and neutral pions are not expected in the final state. However, a small but significant γγ→π0π0 cross section is observed. We demonstrate that this may be accounted for by a rotation in isospin space induced by final-state interactions. The resulting π+π- cross section is in good agreement with experiment, while the π0π0 cross section is in qualitative agreement with the data