Search for T=2 dibaryons in the p→+p→${\mathrm{\pi }}^{\mathrm{-}}$+X reaction and study of highly inelastic NN scattering

In order to search for isospin-2 dibaryons and to study the inelastic nucleon-nucleon channels producing at least two pions, the differential cross sections and analyzing powers have been measured for the p(p→,${\mathrm{\pi }}^{\mathrm{-}}$)X reaction with polarized proton beams of 1.45, 2.1, and 2.7 GeV. The pions were detected at an angle of 13.8° by the SPESIII spectrometer located at Laboratoire National Saturne. No statistically significant evidence for structures corresponding to πNN bound states or six-quark states could be established. However, upper limits to the cross section for such processes are deduced. The data analysis in terms of phase space has shown that as the bombarding energy increases, ${\mathit{N}}^{\mathrm{*}}$N final states have to be taken into account besides the usual NΔ and ΔΔ processes in order to adequately describe our results.