First measurement of the pdashp → ndashn depolarization parameter D0n0n at 546 and 875 MeV /c

The depolarization parameter Donon of the pdashp → ndashn charge exchange reaction has been measured for the first time at the CERN Low Energy Antiproton Ring (LEAR) at two antiproton momenta, 546 and 875 MeV/c. The transverse polarization of the recoil neutron was analyzed using a large-acceptance neutron polarimeter made up of two parallel plastic scintillator planes. D0n0n is usually less than 0.35 which suggests that the spin-spin amplitudes dominate in the scattering matrix. Results are compared with the predictions of various NdashN potential models. The agreement is in general satisfactory.