Relativistic effects in the 3N continuum and the A y puzzle

Abstract

The three-nucleon (3N) Faddeev equation is solved in a Poincare-invariant model of the three-nucleon system. Two-body interactions are generated so that when they are added to the two-nucleon invariant mass operator (rest energy) the two-nucleon S-matrix is identical to the non-relativistic S-matrix with a CD Bonn interaction. Cluster properties of the three-nucleon S-matrix determine how these two-nucleon interactions are embedded in the three-nucleon mass operator. Differences in the predictions of the relativistic and corresponding non-relativistic models for elastic and breakup processes are investigated. Of special interest are the lowering of the Ay maximum in elastic nucleon-deuteron (Nd) scattering below ≈25 MeV caused by the Wigner spin rotations and the significant changes of the breakup cross sections in certain regions of the phase space.