Comparison of (π⁻ d→nn withdσ(π⁺ d→pp) to test charge symmetry in the Δ-region

Abstract

First results on π⁻ d → are reported. The measurements were made using 8 specially designed neutron counters, which were carefully calibratedin situ. The differential cross sections atT _π=142, 180, 217, and 254 MeV were obtained at four angles between 0° and 90°, they are compared to π⁺ d →pp data measured at the same energies and angles with the same setup. At every beam energy, the shape of the angular distributions of π⁻ d →nn and π⁺ d →pp is the same to ±2%. The absolute cross sections differ by 1 to 10%. The error in this comparison is ±4% implying a small violation of charge symmetry.