Hybrid-bubble-chamber study of nucleon diffractive dissociation in 14-GeV/cπ±pcollisions

Two experiments to study the low-mass diffractive enhancement recoiling against a fast forward pion from ${\pi }^{+}p$ and ${\pi }^{-}p$ collisions at 14 GeV/c are described. Photographs of the SLAC 40-in. hydrogen bubble chamber were triggered by a downstream spectrometer when the missing mass, calculated on-line, was above 1.1 GeV. Evidence for a nonresonant mass peak at 1.35 GeV is presented, as well as for production of resonances at about 1.5 and 1.68 GeV. The data are presented as distributions in mass and momentum transfer, as well as moments and isocline plots of the decay angular distributions. Model-independent features are emphasized.