Experimental results on diffractive one-pion production at the CERN ISR

New experimental results are reported on diffractive dissociation of protons into (nπ+) in proton-proton collisions at a center-of-mass energy of √s=45 GeV. The data were obtained using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. The authors have searched for resonance contributions and found peaks at mass values of 1.5 GeV, 1.65 GeV, and 2.1 GeV. A dip in dsigma/dt is observed at low mass; it is most pronounced for events with neutrons emitted at 900 in the Gottfried-Jackson frame. The correlation between mass and slope depends strongly on thetasub(J). The cross section of the channel pp→pnπ+ is 400+-110 μb at √s=45 GeV, giving an energy dependence of ssup(-0.30+-0.07) for isospin exchange zero in this channel. (Auth.)