Abstract
In the framework of nonlinear nuclear models based on the relativistic Hartree-Fock approximation, we have isolated the contribution of the tensor force of pions in the effective NN interaction, by means of two different approximate methods, recently developed by us, in order to dilucidate its role in a variety of nuclear properties. Results show that a reduction of the contribution of this tensor force considerably influences the spin-orbit splittings and magic gaps in the spin-unsaturated midweight 56Ni nucleus as well as the behaviour of the total binding energies with A in heavy nuclei. Both methods give similar results. We also study the evolution of the splitting of the proton 1d spin-orbit doublet in the chain Z=14, from N=20 to N=28, and the neutron 2p − 1f shell in the chain N=28, from the 48Ca nucleus to the 42Si nucleus. Whereas, in the first case, the pion tensor force (PTF) plays an important role and its reduction is needed to reproduce the corresponding experimental results; in the second case, the quenching of the neutron 2p3/2 − 1f7/2 gap in the mentioned isotonic chain N=28 is hardly affected by the PTF.
Highlights
In the framework of nonlinear nuclear models based on the relativistic Hartree-Fock approximation (RHFA), that include pions with a pseudovector coupling for the π-nucleon interaction, we have developed two ways to identify the pion tensor force (PTF) contribution [1, 2]
As the RHFA does not contain this kind of correlations, we think it is justified to reduce by hand the PTF contribution to the energy as done in [1, 2]
In the RHFA, we have shown the influence of the PTF contribution on the sp spectrum of the 56Ni nucleus and the binding energy per particle of the isotopic chain of the lead
Summary
In the framework of nonlinear nuclear models based on the relativistic Hartree-Fock approximation (RHFA), that include pions with a pseudovector coupling for the π-nucleon interaction, we have developed two ways to identify the pion tensor force (PTF) contribution [1, 2]. On one way [1], we have observed that in the limit of the pion mass mπ → 0, the finite range part of the NN interaction generated by pions contributes to the energy only through the PTF This enables us to determine, in an approximate way, the main contribution of this force to the energy. The single-particle (sp) spectra in spin-unsaturated heavy nuclei [1] and the total binding energy of certain isotopic families [2] improve considerably. We apply our models to study the tensor force effect in these two problems
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