He4(π,π’p)3H reaction: Quasifree and resonance scattering

Exclusive $^{4}\mathrm{He}$(${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$,${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$'p${)}^{3}$H spectra in the excitation energy range between 21.5 and 44 MeV in $^{4}\mathrm{He}$ were measured at ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=180 MeV at several pion and proton angles. The cross section ratio ${\mathit{R}}_{\mathrm{\ensuremath{\pi}}\mathit{p}}$=\ensuremath{\sigma}(${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{+}$'p)/\ensuremath{\sigma}(${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$'p) was found to be between 1 and 2 near 22 MeV which is in the region of the ${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${2}^{\mathrm{\ensuremath{-}}}$, T=0 state. Between 25 and 40 MeV in the continuum, which comprises the giant dipole resonance and broad ${2}^{\mathrm{\ensuremath{-}}}$ and ${2}^{+}$ states, ${\mathit{R}}_{\mathrm{\ensuremath{\pi}}\mathit{p}}$ ranges from 0.22 to 45 in sharp contrast to the predicted values of \ensuremath{\approxeq}1 from a model assuming the entire yield is due to the sequential decay of a state of good isospin, and 6 to 9 from a distorted-wave impulse approximation calculation assuming quasifree proton knockout.