THE LARGE MOMENTUM TRANSFER BEHAVIOUR OF MESON-PHOTON TRANSITION FORM FACTORS

It is reported on predictions for the $\pi$-$\gamma$ transition form factor obtained within a perturbative approach which includes 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. Applications of that approach to the $\eta$-$\gamma$ and ${\eta }^{\mathrm{\prime }}$-$\gamma$ transition form factors are discussed as well.