Pion Double-Charge-Exchange Cross-Section Measurements

Abstract

The differential cross section for the pion double-charge-exchange reaction ${\mathrm{V}}^{51}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})$, at an incident energy of 31 MeV and a production angle of 29\ifmmode^\circ\else\textdegree\fi{}, has been measured to be ${0.52}_{\ensuremath{-}0.19}^{+0.71}$ \ensuremath{\mu}b/sr. The apparatus was sensitive to a pion-energy difference of 7 to 19 MeV, which covers the predicted isobaric analog state of $\ensuremath{\Delta}{T}_{Z}=2$. A similar measurement for ${\mathrm{Li}}^{7}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})$ gave a differential cross section of ${0.165}_{\ensuremath{-}0.060}^{+0.225}$ \ensuremath{\mu}b/sr. Particle trajectories were photographed in thin-foil spark chambers. The charge and momenta of outgoing particles were determined with a magnet, and their range was determined in a thick-plate spark chamber.