FIRST MEASUREMENT OF THE P(P)OVER-BAR -] N(N)OVER-BAR DEPOLARIZATION PARAMETER D-0N0N AT 546 AND 875 MEV C/

The depolarization parameter D-OnOn of the ($) over bar pp --> ($) ove r bar nn charge exchange reaction has been measured for the first time at the CERN Low Energy Antiproton Ring (LEAR) at two antiproton momen ta, 546 and 875 MeV/c. The transverse polarization of the recoil neutr on was analyzed using a large-acceptance neutron polarimeter made up o f two parallel plastic scintillator planes. D-OnOn is usually less tha n 0.35 which suggests that the spin-spin amplitudes dominate in the sc attering matrix. Results are compared with the predictions of various ($) over bar NN potential models. The agreement is in general satisfac tory.