Narrow Results

Measurements on the η meson production in proton-deuteron collisions have been performed using the COSY-11 facility at COSY (Jülich). Here we present preliminary results on total and differential cross sections for the pd→³Heη reaction at five excess energies between Q=5.1 and Q=40.6 MeV. The obtained angular distributions for the emitted η mesons in the center of mass system expose a transition from an almost isotropic emission to a highly anisotropic distribution. The extracted total cross sections support a strong η-³He final state interaction and will be compared with model predictions.

The BES collaboration has recently observed a strong enhancement close to the proton-antiproton, threshold in the J/ψ decays into . Such a structure can be explained by a traditional nucleon-antinucleon, , model. The near threshold ¹¹S₀ bound state and/or the well-established ¹³P₀ resonant state found in this interaction can adequately describe the BES data.