One-pion-exchange three-nucleon force and the A_y puzzle

We consider a new three-nucleon force generated by the exchange of one pion in the presence of a 2N correlation. The underlying irreducible diagram has been recently suggested by the authors as a possible candidate to explain the puzzle of the vector analyzing powers A_y and iT₁₁ for nucleon-deuteron scattering. Herein, we have calculated the elastic neutron-deuteron differential cross section, A_y, iT₁₁, T₂₀, T₂₁, and T₂₂ below breakup threshold by accurately solving the Alt-Grassberger-Sandhas equations with realistic interactions. We have also studied how A_y evolves below 30 MeV. The results indicate that this new 3NF diagram provides one possible additional contribution, with the correct spin-isospin structure, for the explanation of the origin of this puzzle.