An analysis of the contribution of isospin two pi-pi resonant statesin the antineutron-proton --> pi+ pi+ pi- annihilation reaction

The results of a search for a possible evidence of a pi+pi+ resonant state in the antineutron-proton --> pi+pi+pi- annihilation reaction with data collected by the OBELIX Experiment are presented. The study has been performed by means of a partial wave analysis in the frame of the isobar model. Production fractions for a possible pi+pi+ resonance have been evaluated. The observed effects at the pi+pi+ threshold may be described reasonably well by the contributions of f2(1270), f0(1500), f2(1565) and rho(1450) states and their interferences, but a meaningful statistical indication for a pi+pi+ scalar state at about 1400 MeV emerges from the analysis.