The gluon content of the $η$ and $η^{\prime}$ mesons and the $ηγ$, $η^{\prime}γ$ electromagnetic transition form factors

Abstract

We compute power-suppressed corrections to the ηγand η^{\prime}γtransition form factors Q^2F_{η(η^{\prime})γ}(Q^2) arising from the end point regions x \to 0,1 by employing the infrared-renormalon approach. The contribution to the form factors from the quark and gluon content of the η,η^{\prime} mesons is taken into account using for the η-η^{\prime} mixing the SU_f(3) singlet η_1 and octet η_8 basis. The theoretical predictions obtained this way are compared with the corresponding CLEO data and restrictions on the input parameters (Gegenbauer coefficients) B_2^q(η_1), B_2^g(η_1), and B_2^q(η_8) in the distribution amplitudes for the η_1,η_8 states with one nonasymptotic term are deduced. Comparison is made with the results from QCD perturbation theory.