Investigation of the reaction pp → pπ⁺π⁺π⁻ n in the double-pion-exchange model: Can pion exchange simulate an exotic state?

Abstract

The reaction pp → pπ⁺π⁺π⁻ n at the incident proton momentum of P _lab=70 GeV/c, where candidates for an exotic baryon were found, is analyzed in the model involving a double exchange of a Reggeized π meson. The model is tested by using available data on the above reaction at P _lab=6.92 and 19 GeV/c. The model provides a satisfactory description of the energy dependence of the reaction cross section. At the same time, it fails to explain the experimentally observed fact that, at P _lab=70 GeV/c, the mass spectrum of the Δ⁺⁺π⁺ system has peaks at 1.42 and 1.64 GeV/c ² in the Feynman variable interval 0.5<x _F(pπ⁺π⁺)<0.8. On the basis of the model in question, upper limits on the cross sections for the production of candidates for the exotic baryon E ₅₅ were estimated at σ_1.42≈2.3 µb and σ_1.64≈1.0 µb.