Resonance degrees of freedom in the two-nucleon system

Abstract

Free nucleon-nucleon scattering is investigated with the explicit treatment of $\ensuremath{\Delta}(1236)$ resonances. The coupled channel problem ($NN+N\ensuremath{\Delta}+\ensuremath{\Delta}\ensuremath{\Delta}$) is solved and compared with the results obtained from perturbation calculations (impulse approximation). The nucleon-nucleon potential used is the Reid-soft-core potential which has been modified according to the phase shift and deuteron binding energy requirements. The perturbation treatment turns out to be not a very good approximation as the $\ensuremath{\Delta}$ admixtures are off up to about 50% in a nonsystematic way.NUCLEAR REACTIONS nucleon-nucleon scattering, resonance admixtures.