Reactions π+p → pπ+π+π-vector-(π0) at 3.94 GeV/c incident momentum: analysis in the framework of the OPER model

The reactions π+p → pπ+π+π-vector-(π0) with π- backward production were studied at 3.94 GeV/c incident momentum making use of the 1.5 m spark spectrometer. The momentum transfer and two- and three-particle (pπ-, pπ+, π+π-, π+π+, pπ-π+, pπ+π+) invariant mass distributions measured in the π+p → pπ+π+π-vector- reaction were analyzed in the framework of the OPER model. It is shown that events with fast proton forward emission corresponding to small invariant masses of the pπ+π- system cannot be described only by the OPER model and should be considered as baryon-exchange processes