Abstract
The Gamow-Teller(GT) states are investigated in relativistic models. The Landau-Migdal(LM) parameter is introduced in the Lagrangian as a contact term with the pseudo-vector coupling. In the relativistic model the total GT strength in the nucleon space is quenched by about 12% in nuclear matter and by about 6% in finite nuclei, compared with the one of the Ikeda-Fujii-Fujita sum rule. The quenched amount is taken by nucleon-antinucleon excitations in the time-like region. Because of the quenching, the relativistic model requires a larger value of the LM parameter than non-relativistic models in describing the excitation energy of the GT state. The Pauli blocking terms are not important for the description of the GT states.
Highlights
For the last 30 years it has been shown that relativistic models work very well phenomenologically to explain various nuclear phenomena[1]
Since the total GT strength in the nucleon space is quenched in the mean field approximation, we expect that the sum of the RPA strengths in finite nuclei is quenched, as in the case of nuclear matter
In 1980’s, analytic expressions of the excitation energies for the giant monopole and quadrupole resonance states were derived in the relativistic model[16]
Summary
For the last 30 years it has been shown that relativistic models work very well phenomenologically to explain various nuclear phenomena[1]. We study the excitation energy and strength of the Gamow-Teller(GT) states in the relativistic models. As far as the authors know, the GT states have not been studied in detail so far[2]. We will discuss those mainly in nuclear matter, since we can obtain analytic expressions of the excitation energy and strength which make clear the structure of the relativistic model and the difference between the relativistic and non-relativistic models. Effects of the Pauli blocking terms on the excitation energy and strength will be shown to be negligible in section IV and V. The last section will be devoted to a brief summary of the present work
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