Relativistic three-body calculations of a Y=1, I=3/2, JP=2+ pi-Lambda-N -- pi-Sigma-N dibaryon

The pi-Lambda-N - pi-Sigma-N coupled-channel system with quantum numbers (Y,I,JP) = (1,3/2,2+) is studied in a relativistic three-body model, using two-body separable interactions in the dominant p-wave pion-baryon and 3S1 YN channels. Three-body equations are solved in the complex energy plane to search for quasibound-state and resonance poles, producing a robust narrow pi-Lambda-N resonance about 10 - 20 MeV below the pi-Sigma-N threshold. Viewed as a dibaryon, it is a 5S2 quasibound state consisting of Sigma(1385)-N and Delta(1232)-Y components. Comparison is made between the present relativistic model calculation and a previous, outdated nonrelativistic calculation which resulted in a pi-Lambda-N bound state. Effects of adding a Kbar-N-N channel are studied and found insignificant. Possible production and decay reactions of this (Y,I,JP)=(1,3/2,2+) dibaryon are discussed.