Isospin invariance in the reaction n + p --> [pi][deg] + d

Abstract

A measurement of the differential cross section for the reaction n + p --> d + [pi][deg] has been made using a neutron beam with kinetic energies up to 720 MeV. The angle and momentum of the deuterons were measured using an analyzing magnet and wire spark chambers with a magnetostrictive readout. The photons from the decaying [pi][deg] were not detected. The neutron energy was calculated from the measured deuteron angle and momentum. The cross sections are compared to those for the reaction [pi]+ + d [left arrow over right arrow] p + p as a test of isotopic spin invariance in strong interactions. The symmetry of the cross sections about 90[deg] is also investigated, and an upper limit of about 1% is placed on the real part of the ratio of isospin-violating to isospin-conserving amplitudes.