Space-Time Symmetry Violation and Neutron-Polarization Rotation

Abstract

P-violating neutron-spin rotation was firstly observed in a p-wave neutron-nucleus resonance. A lanthanum target was placed in a superconducting box. The incident neutron spin was set at transverse direction to the neutron beam in the horizontal plane. The neutron spin rotates around its momentum axis in the presence of P-violating interaction. The neutron spin passes through a Meissner sheet without any change in its direction. The rotation angle was converted to a projection angle on a vertical magnetic field in the downstream, which was analyzed by a polarized ³He neutron polarimeter. The experimental result of the P-violating rotation is consistent with the theory of s- and p-wave parity mixing in the compound nucleus state. For the T-violation experiment, measurement of T-odd triple correlation between the neutron spin, the neutron momentum and the nuclear spin, a new method is proposed, which greatly reduces systematic errors. The experiment can be compared with the neutron electric dipole moment. Target-nucleus polarization was developed for the T-violation experiment by using a dynamic nuclear polarization. A large lanthanum nuclear polarization was obtained.