Measurement of spin observables in neutron-proton elastic scattering

A double scattering experiment, performed at the Paul-Scherrer-Institut (PSI), has measured a large variety of spin observables for free np elastic scattering from 260 to 535 MeV in the c.m. angle range from 60° to 164°. Results are presented for the depolarization parameters \(\) and \(D_{os''ok}\), the polarization transfer parameters \(K_{onno}, K_{os''so}\) and \(K_{os''ko}\), and the 3-index parameters \(N_{onkk}, N_{os''kn}, N_{os''sn}\) and \(N_{os'ʼns}\). The last four parameters have been measured for the first time in this energy range. These measurements considerably improve the data base available for neutron-proton scattering and will allow a direct reconstruction of the I = 0 scattering matrix, providing complete information about the nucleon-nucleon interaction in a model-independent way.