INVESTIGATION OF NUCLEAR-CHARGE SYMMETRY BY PION ELASTIC-SCATTERING FROM H-3 AND HE-3

We have measured differential cross sections for pion elastic scatteri ng from H-3 and He-3 in the angular region near the minimum in the non -spin-flip amplitude. Data were acquired for incident pion energies of 180, 220, 256, and 295 MeV. Nuclear charge symmetry is investigated w ith the aid of several charge-symmetric ratios formed from combination s of measured cross sections. A particularly intriguing result is obta ined from the superratio R, which is defined as R=d sigma(pi(+3)H)d si gma(pi(-3)H)/d sigma(pi(+3)He)d sigma(pi(-3)He). R is found to be grea ter than unity at 180 MeV and significantly smaller than unity at 256 MeV, with the transition occurring at around 210 MeV. The charge-symme try prediction for this ratio (after allowance for the Coulomb force) is one, and is independent of energy and angle.