Meson-Photon Transition Form Factors

Abstract

We report results on the $\pi$-$\gamma$ transition form factor obtained within the hard scattering approach including transverse momentum effects and Sudakov corrections. The results clearly favor distribution amplitudes close to the asymptotic form, $\sim x_1{x}_2$, and disfavor distribution amplitudes which are strongly concentrated in the end-point regions. This observation is backed by information on the elastic form factor of the pion and on its valence quark distribution function. Applications of our approach to the $\eta$-$\gamma$ and ${\eta }^{\prime }$-$\gamma$ transition form factors are discussed as well. Combining the form factor data with the two-photon decay widths, we determine the $\eta$ and the ${\eta }^{\prime }$ decay constants and the $\eta$-${\eta }^{\prime }$ mixing angle.

Comments: 21 pages, REVTEX, 5 figures (appended as uuencoded compressed tar file) preprint WU-B 94-28, BUGH Wuppertal