Browsing by Author "Ren, Xiu-Lei"

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    Consistency between SU(3) and SU(2) covariant baryon chiral perturbation theory for the nucleon mass
    (Elsevier, 2017) Ren, Xiu-Lei; Alvarez-Ruso, L.; Geng, Li-Sheng; Ledwig, Tim; Meng, Jie; Vacas, M. J. Vicente
    Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the 19 low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order [1] is supported by comparing the effective parameters (the combinations of the 19 couplings) with the corresponding low-energy constants in the SU(2) sector [2]. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus providing support to the assumption made in Ref. [2] that the SU(2) baryon chiral perturbation theory can be applied to study nf = 2+1 lattice QCD simulations as long as the strange quark mass is close to its physical value.
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    Relativistic Brueckner-Hartree-Fock theory in nuclear matter without the average momentum approximation
    (American Physical Society, 2018) Tong, Hui; Ren, Xiu-Lei; Ring, Peter; Shen, Shi-Hang; Wang, Si-Bo; Meng, Jie
    Brueckner-Hartree-Fock theory allows one to derive the G matrix as an effective interaction between nucleons in the nuclear medium. It depends on the center-of-mass momentum P of the two particles and on the two relative momenta q and q′ before and after the scattering process. In the evaluation of the total energy per particle in nuclear matter, usually the angle-averaged center-of-mass momentum approximation has been used. We derive in detail the exact expressions of the angular integrations of the momentum P within relativistic Brueckner-Hartree-Fock (RBHF) theory, especially for the case of asymmetric nuclear matter. In order to assess the reliability of the conventional average momentum approximation for the binding energy, the saturation properties of symmetric and asymmetric nuclear matter are systematically investigated based on the realistic Bonn nucleon-nucleon potential. It is found that the exact treatment of the center-of-mass momentum leads to non-negligible contributions to the higher order physical quantities. The correlations between the symmetry energy Esym, the slope parameter L, and the curvature Ksym of the symmetry energy are investigated. The results of our RBHF calculations for the bulk parameters characterizing the equation of state are compared with recent constraints extracted from giant monopole resonance and isospin diffusion experiments.