Analysis of the charge-exchange reaction pp → (pπ+)(pπ−) and of Δ++Δ0 production at the CERN ISR

We present the results of a systematic analysis of charge-exchange double dissociation in proton-proton collisions at the CERN Intersecting Storage Rings. The data, obtained with the Split-Field Magnet detector, cover the entire ISR energy range between s = 23 GeV and s = 63 GeV at five standard energies. Double resonance production is observed in the Δ++Δ0 and Δ++N0(1688) final states. The mass spectra of the pπ− system show more pronounced resonant signals in the backward Jackson hemisphere. A detailed analysis of differential cross sections shows a forward peak typical of absorbed pion exchange decreasing as s−1.81±0.06, followed by a much gentler exponential behaviour associated with a trajectory typical of ϱ-A2 exchange. The high-energy transition to this regime is also indicated by a dramatic change in the s-dependence of total cross sections as compared with low-energy data. Power-law fits in the form sn for all three (pπ+)(pπ−), Δ++Δ0, and Δ++N0(1688) channels reach an s−1 behaviour with exponents n = −1.03 ± 0.01, −0.94 ± 0.01, and n = −1.04 ± 0.01, respectively.