Search

A systematic study has been made of the reactions $\mathrm{pp}\ensuremath{\rightarrow}\mathrm{pp}$ and $\mathrm{pp}\ensuremath{\rightarrow}p{N}^{*}$ in the angular range from ${\ensuremath{\theta}}_{\mathrm{lab}}={10}^{\ensuremath{\circ}}$ to ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}={90}^{\ensuremath{\circ}}$ at 3, 4, 5, 6, and 7 $\frac{\mathrm{GeV}}{c}$. An orthogonal dispersion magnetic spectrometer detected protons from interactions in hydrogen with momentum transfer ($\ensuremath{-}t$) in excess of 0.5 ${(\mathrm{GeV})}^{2}$. Well-defined peaks in the missing-mass spectra occurred at average ${N}^{*}$ masses of 1240\ifmmode\pm\else\textpm\fi{}6, 1508\ifmmode\pm\else\textpm\fi{}2, and 1683\ifmmode\pm\else\textpm\fi{}3 MeV with average full widths of 102\ifmmode\pm\else\textpm\fi{}4, 92\ifmmode\pm\else\textpm\fi{}3, and 110\ifmmode\pm\else\textpm\fi{}4 MeV, respectively. Below 2400 MeV no other significant enhancements were found. The ${N}^{*}$ production cross sections $\frac{d\ensuremath{\sigma}}{\mathrm{dt}}$ near ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}={90}^{\ensuremath{\circ}}$ are in qualitative agreement with the predictions of the statistical model. For each isobar the differential cross section at fixed energy varies as $\mathrm{exp}(\ensuremath{-}\frac{v}{{v}_{0}})$, where $v\ensuremath{\equiv}[\ensuremath{-}\frac{\mathrm{tu}}{(t+u)}]$; ${v}_{0}$ varies systematically with energy and tends toward the same value ($\ensuremath{\approx}0.4$ Ge${\mathrm{V}}^{2}$) for each isobar at the upper limit of our energy range.

We have measured the missing mass spectrum of nucleon isobars produced in the reaction p+p→ +p by 7.1 GeV/c protons incident on a liquid-hydrogen target. Scintillation counters detected the recoil protons after momentum analysis. Cross-sections were obtained for production of isobars of mass 1238, 1512 and 1688 MeV at momentum transfers of 0.09, 0.15, 0.24, 0.33, and about 5 (GeV)2. At low momentum transfers, the spectrum has additional structure at a mass of about 1430 MeV. TheT=1/2 isobar production cross-sections at |t|=5 (GeV)2 are comparable with the elastic scattering cross-section.