  The quenching factor of the proton recoil in the stilbene scintillator was
measured with a 252Cf neutron source and was found to be 0.1 - 0.17 in the
recoil energy range between 300 keV and 3 MeV. It was found to depend on the
direction of the recoil proton. The directional anisotropy of the quenching
factor could be used to detect the wind of the WIMPs caused by the motion of
the earth around the galactic center.
