Isobar Production and Elastic Scattering inp−pInteractions from 6 to 30GeVc

Abstract

Differential cross sections have been measured for nucleon-isobar production and elastic scattering in $p\ensuremath{-}p$ interactions from 6.2 to 29.7 $\frac{\mathrm{GeV}}{c}$ in the laboratory angle range $8l{\ensuremath{\theta}}_{\mathrm{sc}}l265$ mrad. ${N}^{*}$' s at 1236, 1410, 1500, 1690, and 2190 MeV were observed. Computer fits to the mass spectra under varying assumptions of resonance and background shapes show that conclusions on $t$ and $s$ dependence are only slightly affected despite typical variations in absolute normalization of \ifmmode\pm\else\textpm\fi{} 35%. Logarithmic $t$ slopes in the small- $|t|$ range are $\ensuremath{\sim}15 {(\frac{\mathrm{GeV}}{c})}^{\ensuremath{-}2}$ for the ${N}^{*}(1410)$, $\ensuremath{\sim}5 {(\frac{\mathrm{GeV}}{c})}^{\ensuremath{-}2}$ for the ${N}^{*}$'s at 1500, 1690, and 2190 MeV, and $\ensuremath{\sim}9 {(\frac{\mathrm{GeV}}{c})}^{\ensuremath{-}2}$ for elastic scattering. Also for the small- $|t|$ data, cross sections for ${N}^{*}$'s at 1410, 1500, 1690, and 2190 MeV and for elastic scattering vary only slightly with ${P}_{\mathrm{inc}}$ consistent with the dominance of Pomeranchuk exchange and with diffraction dissociation. A fit of ${N}^{*}(1690)$ total cross sections to the form ${\ensuremath{\sigma}}^{\ensuremath{\propto}}{P}^{\ensuremath{-}n}$ gives $n=0.34\ifmmode\pm\else\textpm\fi{}0.06$, while for elastic scattering $n=0.20\ifmmode\pm\else\textpm\fi{}0.05$. For the ${N}^{*}(1690)$ the effective Regge trajectory has the slope ${{\ensuremath{\alpha}}_{\mathrm{eff}}}^{\ensuremath{'}}(0)=0.38\ifmmode\pm\else\textpm\fi{}0.17$. When compared with ${N}^{*}$ production in ${\ensuremath{\pi}}^{\ensuremath{-}}$, ${K}^{\ensuremath{-}}$, and $\overline{p}$ beams these data also agree with approximate factorization of the Pomeranchuk trajectory. ${N}^{*}(1236)$ cross sections are consistent with other measurements at similar momenta. For $\ensuremath{-}tg1 {(\frac{\mathrm{GeV}}{c})}^{\ensuremath{-}2}$, elastic scattering cross sections decrease approximately as ${{P}_{\mathrm{inc}}}^{\ensuremath{-}2}$, and they and ${N}^{*}(1500)\ensuremath{-}$ and ${N}^{*}(1690)\ensuremath{-}$ production cross sections have $t$ slopes consistent with 1.6 ${(\frac{\mathrm{GeV}}{c})}^{\ensuremath{-}2}$.