Energy-Dependence of the Nucleon Self-Energies in Off-Mass-Shell Energy   Region and the Gamow-Teller Sum-Rule in the Relativistic Hartree-Fock   Approach
  The relativistic Hartree approximation predicts a deep attractive potential for antinucleon, which largely reduce the threshold energies of the nucleon-antinucleon (N-Nbar) production. This effect has played an important role to explain the quenching of the Gamow-Teller (GT) strength because the quenched strength in the particle-hole excitation is partially taken by the nucleon-antinucleon production. On the other hand antiproton experiments do not reveal deep attractive potential for antinucleon. In this paper we study energy-dependence of the nucleon self-energies in the relativistic Hartree-Fock (RHF) approximation in off-mass-shell states. Then we demonstrate that the antinucleon appearing in low energy observables is in the off-mass-shell energy region and its properties are quite different from that at the on-mass-shell state. Furthermore we show that the quenched amount of the GT strength is not taken only by the \NNbar production but also by the meson production through the imaginary part of the nucleon self-energy in the RHF approximation. 
Tomoyuki Maruyama