Three-nucleon forces in neutron-deuteron elastic and inelastic scattering*

The sensitivity to three-nucleon forces (3NF) of nucleon-deuteron elastic scattering at large center-of-mass angles is by now well known. Previous p-d experiments (differential cross sections and spin observables) have tended to agree better with calculations that include 3NF, although at energies 200 MeV and above both p-d and n-d cross sections exceed theoretical predictions. We have undertaken a measurement of the dependence on incident neutron energy of the differential cross section for n-d elastic scattering and will report data in the range 130-250 MeV. The sensitivity of the inelastic process d(N,Nnp) to 3NF is not as clear from the calculations; effects are seen to be generally small and to depend strongly on kinematics and on the form of the 3NF used. The theoretical inelastic cross sections in quasi-free kinematics exhibit almost no sensitivity to 3NF, but are not able to reproduce the only data available (d(p,np)p at 200 MeV) in the intermediate energy region. To investigate this problem and to motivate further theoretical work, we have undertaken a measurement of the energy dependence of the d(n,np)n cross section in the incident energy range 100-400 MeV.