Central exclusive meson pair production in the perturbative regime
  We present a study of the central exclusive production (CEP) of meson pairs, MMbar, at sufficiently high invariant mass that a perturbative QCD formalism is applicable. Within this framework, MMbar production proceeds via the gg --> MMbar hard scattering sub-process, which can be calculated within the hard exclusive formalism. We present explicit calculations for the gg --> MMbar helicity amplitudes for different meson states and, using these, show results for meson pair CEP in the perturbative regime. 
L.A. Harland-Lang, V.A. Khoze, M.G. Ryskin, W.J. Stirling
hep-ph