INVESTIGATION OF THE REACTION DP-]PP(+)NN

The reaction dp --> p pi(+)nn induced by 3.34-GeV/c deuterons is inves tigated under experimental conditions of 4 pi geometry. The reaction i s shown to proceed mostly via the quasinucleon-nucleon transition pp - -> pn pi(+) accompanied by a spectator neutron. The anisotropy of neut ron emission in quasiproton-proton collisions results in the invariant mass of two neutrons (the missing mass for the reaction under investi gation) populating two distinct mass regions. Thereby, interactions oc curring at the proton and deuteron vertices are naturally separated. A s soon as off-mass-shell effects are disregarded, the ''neutron mass'' estimated from data on quasinucleon-nucleon collisions is found to be significantly distorted in an asymmetric way. The observation that De lta isobars emitted from the proton and deuteron vertices are characte rized by different parameter values is qualitatively interpreted.