NUCLEON ISOBAR PRODUCTION IN PROTON-PROTON COLLISIONS BETWEEN 3 AND 7 GEV/C

A systematic study has been made of the reactions pp→pp and pp→pN* in the angular range from θlab=10 to θc.m.=90 at 3, 4, 5, 6, and 7 GeVc. An orthogonal dispersion magnetic spectrometer detected protons from interactions in hydrogen with momentum transfer (-t) in excess of 0.5 (GeV)2. Well-defined peaks in the missing-mass spectra occurred at average N* masses of 1240±6, 1508±2, and 1683±3 MeV with average full widths of 102±4, 92±3, and 110±4 MeV, respectively. Below 2400 MeV no other significant enhancements were found. The N* production cross sections dσdt near θc.m.=90 are in qualitative agreement with the predictions of the statistical model. For each isobar the differential cross section at fixed energy varies as exp(-vv0), where v[-tu(t+u)]; v0 varies systematically with energy and tends toward the same value (0.4 GeV2) for each isobar at the upper limit of our energy range. © 1968 The American Physical Society.