A measurement of the plus/minus ratio for the production of pions by alpha-particles incident on carbon nuclei has been carried out to test the charge symmetry hypothesis. Employing an experimental procedure which eliminates residual errors in geometry, etc., the ratio was found to be 0.72±0.17. The alpha-particle energy was 375 Mev and the meson energy was 15 Mev observed at 90° to the beam. Coulomb effects are expected to bring about a depression of the production ratio from unity of about this magnitude. The experimental result, therefore, provides support for the charge symmetry hypothesis.

As supplementary information the same apparatus was used to measure the pion plus/minus ratio for 330-Mev protons incident on carbon. The ratio found was 5.4±0.8.

• Received 24 October 1952

DOI:https://doi.org/10.1103/PhysRev.89.758