Nd breakup process in leading order in a three-dimensional approach

A three-dimensional approach based on momentum vectors as variables for solving the three-nucleon Faddeev equation in first order is presented. The nucleon-deuteron breakup amplitude is evaluated in leading order in the nucleon-nucleon (NN) T matrix, which is also generated directly in three dimensions avoiding a summation of partial wave contributions. A comparison of semiexclusive observables in the d(p, n)pp reaction calculated in this scheme with those generated by a traditional partial wave expansion shows perfect agreement at lower energies. At about 200 MeV nucleon laboratory energies deviations in the peak of the cross section appear, which may indicate that special care is required in a partial wave approach for energies at and higher than 200 MeV. The role of higher order rescattering processes beyond the leading order in the NN T matrix is investigated with the result that at 200 MeV rescattering still provides important contributions to the cross section and certain spin observables. The influence of a relativistic treatment of the kinematics is investigated. It is found that relativistic effects become important at projectile energies higher than 200 MeV.