Two-photon processes of pseudoscalar mesons in a Bethe-Salpeter approach

Abstract

We evaluate the ${\pi }^0{\gamma }^{\ast }\to \gamma$ transition form factor and $\gamma \gamma$ decay widths for ${\pi }^0,{\eta }_c$ and ${\eta }_b$ treated as $q\bar{q}$ bound states in the Bethe-Salpeter formalism, incorporating the dynamical chiral symmetry breaking and the Goldstone nature of the pion. In the chiral limit, the Abelian axial anomaly is incorporated analytically in our coupled Schwinger-Dyson and Bethe-Salpeter approach, which is also capable of quantitatively describing systems of heavy quarks, concretely ${\eta }_c$ and possibly ${\eta }_b$.

Comments: RevTeX style, 15 pages, 1 PS figures, uses epsf.sty, minor revisions of the text, small additions to the table and to one figure, comments on new references