[Formula Presented] reaction near threshold

We calculated the differential and total cross sections of the reaction [Formula Presented] near threshold taking into account all the single- and double-scattering graphs within a relativistic formalism. The net effect of the second order diagrams is very small since there is a strong cancellation between the pion-exchange diagram and the sum of the η exchange with the nucleon-nucleon final state interaction diagrams. Our theoretical results are compared with recent experimental data for the differential yield, corresponding to the counting rate for the detection of the two photons into which the produced η decays. The quality of the agreement between theory and existing data between 35 and 100 MeV above threshold does not indicate, at those energies, effects of a possible [Formula Presented] quasibound state.