Pion Double-Charge-Exchange Cross-Section Measurements

The differential cross section for the pion double-charge-exchange reaction ${\mathrm{V}}^{51}({\pi }^{+}, {\pi }^{-})$, at an incident energy of 31 MeV and a production angle of 29°, has been measured to be ${0.52}_{-0.19\mathrm{}}^{+0.71\mathrm{}}$ μb/sr. The apparatus was sensitive to a pion-energy difference of 7 to 19 MeV, which covers the predicted isobaric analog state of $\Delta T_Z=2\mathrm{}$. A similar measurement for ${\mathrm{Li}}^7({\pi }^{+}, {\pi }^{-})$ gave a differential cross section of ${0.165}_{-0.060\mathrm{}}^{+0.225\mathrm{}}$ μb/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.