2-Pion Production In Pn Collisions At 11.6 Gev-C

Two-pion production in pn reactions is studied in pd collisions at 11.6 GeV/ c . In particular the final state pn π + π − is analyzed. A cross section of σ = 0.68 ± 0.07 mb is found for the reaction pn → Δ ++ Δ − . Using other data at different energies and assuming I = 1 exchange dominates, the energy dependence of this channel is given by LAB −1.45 . The t ′ distributions for Δ ++ Δ − is described by an absorptive one-pion exchange moddel. The cross section of the exotic exchange reaction pn→ Δ − Δ ++ (with forward Δ − ) a two standard deviation upper limit of 19μb. The final states Δ ++ π − n and Δ − π + p are in agreement with a double Regge pole model with pion and pomeron exchanges. A reggeized one-pion exchange model using experimental π p phase-shift parameters accounts for the gross features of the pn π + π − final state with the p forward and the n backward in the c.m.