SEARCHES FOR A NARROW RESONANCE IN THE PP-PI(-) SYSTEM

The pp pi system whose quantum numbers may assume values that are forb idden for the NN system is investigated for the first time in the reac tion pp --> pp pi(-)pi(+). The experiment was performed at ITEP (Mosco w). The invariant-mass distribution of the pp pi(-) system reveals a r esonance enhancement at M approximate to 2.06 GeV with a width about 1 0 MeV. The observed enhancement may signal the formation of a resonanc e state predicted by quark models and required for interpreting data o n low-energy pion-nucleus scattering accompanied by double charge exch ange.