SEARCH FOR DIBARYONS IN THE P-]P+P+PI- REACTION WITH A BACKWARD PION AT 1.98 GEV(N)C/

The two-proton invariant mass spectrum in the p + n --> p + p + pi- tr ansition with a backward pi- is investigated. The data from the ITEP 3 -meter magnetic spectrometer irradiated by the 1.98 GeV/c proton beam are used. Liquid deuterium serves as a target, and approximately 17000 events contribute to the mass spectrum. No statistically significant narrow dibaryon signals are found in the two-proton invariant mass int erval from 1.89 to 2.17 GeV/c2, and an upper limit on the cross sectio n of production of narrow dibaryons is obtained in the entire mass int erval under study. A narrow enhancement is found near 1.8775 GeV/c2, w hich can be interpreted as a virtual level of the two-proton system.