  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 $iT_{11}$ for nucleon-deuteron
scattering. Herein, we have calculated the elastic neutron-deuteron
differential cross section, $A_y$, $iT_{11}$, $T_{20}$, $T_{21}$, and $T_{22}$
below break-up 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.
