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Investigation of nuclear charge symmetry by pion elastic scattering from 3H and 3He

We have measured differential cross sections for pion elastic scattering from 3H and 3He 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 with the aid of several charge-symmetric ratios formed from combinations of measured cross sections. A particularly intriguing result is obtained from the superratio R, R is found to be greater than unity at 180 MeV and significantly smaller than unity at 256 MeV, with the transition occurring at around 210 MeV. The charge-symmetry prediction for this ratio (after allowance for the Coulomb force) is one, and is independent of energy and angle.

differential cross sections ; pion elastic scattering ; nuclear charge symmetry

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