In this paper, we have calculated the equation of state of asymmetric nuclear matter using the lowest order constrained variational approach and Argonne family potentials with and without three-nucleon interaction(TNI) contribution. In particular, we have used the AV18 potential and the re-projected potentials, AV8′, and AV6′. We have also calculated the saturation properties of symmetric nuclear matter, and the nuclear symmetry energy using AV18 +TNI, AV8′+TNI and AV6′+TNI potentials. The inclusion of TNI has modified the agreement with experiment. We have also made a comparison between our results and those of other many-body calculations.
In the framework of a non-relativistic quark model, we have calculated the masses of the \textcolor{red}{$QQ\bar{Q'}\bar{Q'}$} ($Q = c,b,s$ and $ \textcolor{red}{\bar Q'= \bar c, \bar b,\bar s}$) tetraquark states. Using the linear and quadratic confinement potentials inside a Cornell-type potential along with all possible spin and color configurations, the Schroedinger equation masses of these tetraquark states have been calculated. Based on our numerical analysis, linear confinement and quadratic confinement produce acceptable results. Models that use linear confinement estimated charmonium-like tetraquark mass close to experimental data, as well as bottomonium-like tetraquark mass below the threshold of their meson-meson channels.
It has been found in previous works [M. Baldo and K. Fukukawa, Phys. Rev. Lett. 113, 241501 (2014); K. Fukukawa, M. Baldo, G. F. Burgio, L. Lo Monaco and H.-J. Schulze, Phys. Rev. 92, 065802 (2015)] that the nucleon–nucleon potential of [Y. Fujiwara, M. Kohno, C. Nakamoto and Y. Suzuki Phys. Rev. C 64, 054001 (2001); Y. Fujiwara et al., Phys. Rev. C 65, 014002 (2001)] gives an accurate saturation point in symmetric nuclear matter once the three hole-line contributions are included in the Brueckner–Bethe–Goldstone expansion without the addition of three-body forces in the nuclear Hamiltonian. The potential is based on a quark model of nucleons and on the quark–quark interaction together with quark exchange processes. These features introduce an intrinsic nonlocality of the nucleon–nucleon interaction. In order to clarify the role of the quark degrees of freedom and of the nonlocality in the saturation, we perform a comparative study of this potential and the traditional meson exchange models, exemplified in the CD-Bonn potential. We find that at the Brueckner–Hartree–Fock approximation, which corresponds to the two hole-line level of approximation, the dominant modification of the nucleon–nucleon interaction with respect to CD-Bonn is incorporated in the s-wave channels, where the quark degrees of freedom should be more relevant, in particular for the short range quark exchange processes. However, when the three hole-line contribution is included, we find that the higher partial waves play a relevant role, mainly in the term that describes the effect of the medium on the off-shell propagation of the nucleon.
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