Formation of a single pion in antiproton-proton collisions at an incident momentum of 22.4 GeV/c

The emission of a single pion in antiproton-proton interactions induced by 22.4GeV/c antiprotons is found to proceed through the formation and decay of (anti)nucleon resonances. The effective-mass spectrum of the pion-nucleon system is dominated by the delta isobar below 1.35 GeV/c(2) and by the N-1525 and N-1688 resonances above 1.35 GeV/c2. The squared-momentum-transfer distributions for the formation of isospin-3/2 and isospin-1/2 resonances show exponential forms with slope parameters of some 10 and 5 (GeV/c)(-2), respectively.