Q2dependence of exclusive meson production in two-photon reactions

Abstract

We calculate the amplitudes for $e^{+}$ $e^{\mathrm{-}}$→$e^{+}$ $e^{\mathrm{-}}$ MM¯ at large angle as a function of the invariant masses $q_a$ ${\mathrm{}}^2$ and $q_b$ ${\mathrm{}}^2$ of the two virtual photons. We demonstrate that the $q_a$ ${\mathrm{}}^2$ and $q_b$ ${\mathrm{}}^2$ dependence provides highly detailed tests of the applicability of QCD to predictions of exclusive large-angle processes. In addition, at moderate energies the $q^2$ dependence may be used to unambiguously distinguish between possible vector-meson-dominated (i.e., purely hadronic) contributions and those arising from the asymptotically dominant pointlike-photon couplings. We present analytic forms for all relevant amplitudes.