Measurement of the cross section of the reaction pn → ppπ− in the energy region of dibaryon resonances (500–1000 MeV)

The cross section of the reaction pn → ppπ^? has been measured in a deuterium bubble chamber at 9 incident energies in the range 500–1000 MeV. The energy dependence of the isoscalar cross section of single pion production is obtained. It is shown, that if an isoscalar dibaryon resonance exists with the mass in the range 2.17–2.30 GeV its elasticity should be smaller than the theoretical predictions available.