Microscopic K-matrix approach to problem of continuous spectrum for four nucleons

A number of two-particle reactions in four-nucleon system is considered in framework of the multichannel K-matrix method, approximating the K-matrix elements by the exact Born terms in integral equations for four nucleons. A satisfactory agreement with experiment is obtained for scattering into the backward hemisphere at low and intermediate energies for all the reactions, excluding D(d,d)D. A systematic investigation of accuracy of various approximations, used frequently at theoretical description of nuclear reactions in framework of various models, is fulfilled