A bubble-chamber experiment in which the reaction π−+p→π+π+N was studied at a beam momentum of 2.14 BeV/c yielded 1533 and 2234 events of the final states π−π0p and π−π+n, respectively. These events are dominated by the formation of the ρ resonance, which is produced mostly in the forward direction. Both the production and decay angular distributions of the ρ− agree very well with the predictions of the one-pion exchange theory modified by absorption effects. The decay angular distribution of the ρ0 shows the well-known forward-backward asymmetry. This effect is interpretable as the result of the interference between the ρ0 and an isospin-zero s-wave π−π resonance. The production of the ρ0, in addition to its forward peak, shows a weak backward peak. Partial cross sections of various final states are also presented.
We have studied neutral final states produced in π−p collisions at momenta of 1.71, 1.89, 2.07, 2.27, and 2.46 GeVc, by observing the γ rays emitted. In particular, measurements are presented of (i) π−p→π0n, for which the Regge-pole fit at momenta ≥5.9 GeVc also agrees rather well here; (ii) π−p→η0n, for which the Regge model which fits at higher energies does not agree here; (iii) π−p→π0γn, in which there is some evidence for a diffraction dissociation process as well as ω0-meson production; (iv) π−p→π0π0n, which is dominated by production of N*0(1236)π0 and by peripheral production of pion pairs. In (iv), the former process is found to fit with the same Reggeized ρ-meson exchange model as charge-exchange scattering, while the latter gives indication of the s-wave ππ interaction. An account is given of new techniques, particularly in the data analysis, which were developed in the course of this work.
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