  A model for exclusive diffractive resonance production in proton-proton
collisions at high energies is presented. This model is able to predict double
differential distributions with respect to the mass and the transverse momentum
of the produced resonance in the mass region $\sqrt{M^2}\le$5 GeV. The model is
based on convoluting the Pomeron distribution in the proton with the
Pomeron-Pomeron-meson total cross section. The Pomeron-Pomeron-meson cross
section is saturated by direct-channel contributions from the Pomeron as well
as from two different $f$ trajectories, accompanied by the isolated f$_0(500)$
resonance dominating the $\sqrt{M^{2}} \leq $ GeV region. A slowly varying
background is taken into account.
