Relativity and the low-energy $\mathit{nd}$ ${A}_{y}$ puzzle

Relativity and the low-energy $nd$ $A_{y}$ puzzle

H. Witała, J. Golak, R. Skibiński, W. Glöckle, W. N. Polyzou, and H. Kamada

Phys. Rev. C 77, 034004 – Published 27 March 2008

Abstract

We solve the Faddeev equation in an exactly Poincaré invariant formulation of the three-nucleon problem. The dynamical input is a relativistic nucleon-nucleon ( $NN$ ) interaction that is exactly on-shell equivalent to the high-precision CD Bonn $NN$ interaction. $S$ -matrix cluster properties dictate how the two-body dynamics is embedded in the three-nucleon mass operator (rest Hamiltonian). We find that for neutron laboratory energies above $\approx 20$ MeV relativistic effects on $A_{y}$ are negligible. For energies below $\approx 20$ MeV dynamical effects lower the nucleon analyzing power maximum slightly by $\approx 2 %$ and Wigner rotations lower it further up to $\approx 10 %$ , thereby increasing disagreement between data and theory. This indicates that three-nucleon forces (3NF) must provide an even larger increase of the $A_{y}$ maximum than expected up to now.