Neutron-deuteron analyzing power data at $E_{n} = 22.5$ MeV

We present measurements of n-d analyzing power, $A_{y}\left ( \theta \right )$, at $E_{n} = 22.5$ MeV. The experiment uses a shielded neutron source which produced polarized neutrons via the $^{2}H\left ( \vec{d},\vec{n} \right )^{3}He$ reaction. It also uses a deuterated liquid-scintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a window in the center detector pulse-height spectrum. The beam polarization is monitored by using a high-pressure helium gas cell and an additional pair of liquid-scintillator side detectors. The $n-d A_{y}\left ( \theta \right )$ data were corrected for finite-geometry and multiple-scattering effects using a Monte Carlo simulation of the experiment. The 22.5-MeV data demonstrate that the three-nucleon analyzing power puzzle also exists at this energy. They show a significant discrepancy with predictions of high-precision nucleon-nucleon potentials alone or combined with Tucscon-Melbourne or Urbana IX three-nucleon forces, as well as currently available effective-field theory based potentials of next-to-next-to-next-to-leading order.