Experimental study of the double charge exchange reaction π + + + 2 4 He→π − +4p between 1.5 and 2.0 GeV/c

The double charge exchange reaction 2 4 He(π+,π−)4p has been studied with helium bubble chamber pictures at 1.46, 1.72 and 1.86 GeV/c incident momenta. Results are presented about crosssections, momentum spectra, angular and effective-mass distributions. The main features observed in this reaction are the low rate of events involving two spectator protons, the quasi-isotropic angular distribution of the negative pion and the abundant Δ(1232) and Δ(1670) resonance production.