Investigationof the np → npπ+π– Reaction at Momenta P0 > 3 GeV/c

The $$np \to np{{\pi }^{ + }}{{\pi }^{ - }}$$ reaction is investigated at the incident neutron momenta $${{P}_{0}}$$ = 3.83 and 5.20 GeV/c. Contributions of different diagrams to the reaction cross section are calculated at the momenta from the threshold to 12 GeV/c. It is shown that the main contributions to the $$np \to np{{\pi }^{ + }}{{\pi }^{ - }}$$ reaction at momenta above $${{P}_{0}}$$ > 3 GeV/c come from diagrams of the reggeized $$\pi $$ -meson exchange model (OPER).To study spin effects, the reaction $$np \to np{{\Delta }^{{ + + }}}{{\Delta }^{ - }}$$ was separated. It is shown that description of the spin density matrix [ $${{\rho }_{{ij}}}$$ ] requires taking into account the ρ-meson exchange diagram. The reaction $$np \to np{{\rho }^{0}}$$ is separated by background subtraction method. The investigation has shown that $${{\rho }^{0}}$$ -meson production is described by suspended diagrams of the OPER model.