Isobaric Analog States in Pion Single-Charge-Exchange Reactions on and above the (3,3) Resonance Energy

The 0° differential cross sections of (π⁺, π⁰) reactions on a series of nuclei to isobaric analog states were determined at 165, 230, and 295 MeV. For each energy, the A dependence is well described by a power law of the form σ=g(E)(N-Z)A^-α(E), where α(E) is a decreasing function of energy. The 0° excitation functions peak around the (3,3) resonance energy for all nuclei except ⁹⁰Zr. A possible explanation in terms of neutron and proton densities is discussed.