Experimental Comparison Between On- and Off-Mass-Shell Inelasticities in π^{-}p Scattering

We have investigated the mass spectra of the systems recoiling against peripherally produced ${\Delta }^{++}$ for the reactions $\mathrm{pp}\to {\Delta }^{++}p{\pi }^{-}$, $\mathrm{pp}\to {\Delta }^{++}p{\pi }^{-}{\pi }^0$, and $\mathrm{pp}\to {\Delta }^{++}n{\pi }^{+}{\pi }^{-}$ at 6.6 GeV/c. The experimental cross-section ratios of these systems are found to be comparable with the known on-mass-shell cross section ratios $\sigma ({\pi }^{-}p\to {\pi }^{-}p):\sigma ({\pi }^{-}p\to {\pi }^{-}p{\pi }^0):\sigma ({\pi }^{-}p\to {\pi }^{-}n{\pi }^{+})$ as a function of mass of the system $m\lesssim 1.8$ GeV. This result is compatible with a one-pion-exchange interpretation for the production of the peripheral ${\Delta }^{++}$ component in these five-body states and furthermore suggests that $\pi \pi$ and $K\pi$ inelastic scattering may be realistically studied in the same way.