SECONDARY INTERACTION OF THE PI+ MESON AND THE DELTA++(1232) ISOBAR IN THE REACTION PI+P-]P2-PI+PI- - EXOTIC BARYON RESONANCES

The region of small invariant masses of the p2-pi+ system, produced in the reaction pi+p --> p2-pi+pi- at a beam momentum of 4.2 GeV/c, has been studied. The experimental data in this region are interpreted as evidence of exotic baryon resonances E + + + with isospin 5/2. The masses and widths of these resonances are close to the values found previously in baryon exchange reactions. The total cross section for the production of exotic resonances is 15.3 +/- 2.1-mu-b. A secondary interaction of the pi+ meson and the DELTA + + isobar in the final state is suggested as a mechanism for the production of these resonances. An upper limit of 15 +/- 2-mu-b is estimated for the cross section for the secondary interaction, which occurs in a nonresonance manner. The secondary-pi+ DELTA + + interaction thus occurs through the formation of exotic E + + + baryons in at least 50% of the cases.