Some issues in elementary particle physics involving low-energy neutrons and antiprotons focusing on measurement of violated symmetry

The report addresses the observation of violation of the P, T, CP and CPT symmetries by means of ultra-low energy neutrons and antiprotons, focusing on the measurement of the electric dipole moment of neutrons, observations of P and T nonconservation in resonance absorption reaction, study on CP nonconservation in antiproton-proton annihilation reaction, and feasibility of measuring the gravity imposed on antiprotons. P and T nonconservation occurs if an elementary particle has an electric dipole moment. The electric dipole moment of neutrons can be measured very accurately, providing a useful means of determining the T nonconservation. Ultra-cold neutrons recently have been used for this purpose. P and T nonconservation can be examined also by means of nuclear reactions. In a neutron reaction, T nonconservation can be studied by measuring the degree of asymmetry in the scattering cross section while keeping the direction of the neutron spin perpendicular to that of the target nuclear spin in the plane perpendicular to the beam. (N.K.)