Low-energy pion scattering to 1(-) states in 12C.

Abstract

Differential cross sections for 40, 50, and 65 MeV ${\mathrm{\ensuremath{\pi}}}^{+}$ and ${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$ inelastic scattering to ${1}^{\mathrm{\ensuremath{-}}}$ excitations in $^{12}\mathrm{C}$ have been measured and compared to distorted wave impulse approximation (DWIA) reaction model predictions. Strengths are presented in terms of sum rules for the ${1}^{\mathrm{\ensuremath{-}}}$ state at 10.84 MeV and for the giant dipole resonance from 18 to 25 MeV. An excitation function at q=224 MeV/c for the ${1}^{\mathrm{\ensuremath{-}}}$ state at 10.84 MeV is displayed in the energy range from 50 to 291 MeV showing a non-spin-flip pattern. We find inadequacies in the detailed comparison of the shapes of the data to DWIA calculations using several standard nuclear models.