Predictions of striking energy and angular dependence in pp→(pp)S-waveπ0 production

A phenomenological calculation from threshold to 800 MeV of the initial proton beam energy is presented to describe recent data on the reaction pp→(pp)S-waveπ0 with a low energy cut on the final state diproton excitation energy. A strong forward dip is obtained in the differential cross section as in the data from COSY at 800 MeV, although the absolute value of the forward cross section is too low. Earlier low energy data from Celsius are reasonably well reproduced. In the unexplored energy interval between these two experiments the model predicts a spectacular energy dependence both in the forward direction and in the angle-integrated cross section, which may be related to a delicate interplay of the Δ(1232) and NN background in different interfering partial wave amplitudes.