Pion double charge exchange and inelastic scattering on 3 He

Measurements were made of the doubly differential cross sections for three inclusive pion reactions on ${}^{3}$He: ${\ensuremath{\pi}}^{\ensuremath{-}}$ double charge exchange (DCX), and ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ inelastic scattering. The cross sections for DCX were measured at incident pion energies of 120, 180, and 240 MeV, and at angles of 25$\ifmmode^\circ\else\textdegree\fi{}$, 50$\ifmmode^\circ\else\textdegree\fi{}$, 80$\ifmmode^\circ\else\textdegree\fi{}$, 105$\ifmmode^\circ\else\textdegree\fi{}$, and 130$\ifmmode^\circ\else\textdegree\fi{}$, while inelastic scattering cross sections were measured at 120, 180, and 240 MeV and scattering angles of 50$\ifmmode^\circ\else\textdegree\fi{}$, 80$\ifmmode^\circ\else\textdegree\fi{}$, 105$\ifmmode^\circ\else\textdegree\fi{}$, and 130$\ifmmode^\circ\else\textdegree\fi{}$. In each case the outgoing pion energy spectra were measured from 10 MeV up to the kinematic limit. The DCX spectra exhibit a double-peaked structure at forward angles that can be understood as a consequence of a sequential single charge exchange mechanism. Model calculations based on this mechanism are in rough agreement with the measured spectra. The doubly differential cross sections measured for the inelastic scattering reactions exhibit a prominent quasielastic peak. A distorted-wave impulse-approximation calculation of the quasielastic cross sections has been performed and a comparison made with the measurements.