Isopin invariance in the reaction np --> [pi]0d

Abstract

A measurement of the differential cross section for the reaction np--> [pi]0d has been made at the Lawrence Radiation Laboratory 184-inch cyclotron. A neutron beam with kinetic energies up to 720 MeV was incident on a liquid hydrogen target. The angle and momentum of the deuterons were measured using an analyzing magnet and wire spark chambers with a magnetostrictive readout. Deuterons were separated from protons by time-of-flight. The photons from the decaying [pi]0 were not detected. The neutron energy was calculated from the measured deuteron angle and momentum.Out of 5 x 105 events recorded, 1.1 x 105 events were the desired [pi]0d reaction. The cross sections were compared to those for the reaction [pi]+d --> pp as a test of isotopic spin invariance in strong interactions. The symmetry of the cross sections about 90[deg] was also investigated, and an upper limit of about 1% was placed on the real part of the ratio of isospin-violating to isospin-conserving amplitudes.