arXiv subjects

Xin-le Shang

Publications and source records attributed to Xin-le Shang.

3 recordsLinked to original sources

arXiv2026

Impact of neutron-proton pairing on the nucleon high-momentum distribution in symmetric nuclear matter

The effect of neutron-proton ($np$) pairing on the high-momentum tail (HMT) of nucleon momentum distributions in symmetric nuclear matter is investigated within a combined framework of the extended Brueckner-Hartree-Fock approach with off-shell BCS theory. The HMT ratio, quantifying the high-momentum fraction in the BCS state relative to the normal state, reaches about $1.06$ around the density of $0.052\ \mathrm{fm}^{-3}$, indicating that the maximal contribution of the $np$ pairing, amounts to approximately 6\% that from short-range correlations (SRCs). This contribution exhibits a density dependence that closely follows the squared relative pairing gap $\widetildeΔ_F=Z_FΔ(k_F)$ with respect to the kinetic energy $E_{k_F}^*$ evaluated using the effective mass, suggesting that $\widetildeΔ_F^2/E_{k_F}^{*2}$ provides a qualitative measure of the $np$ pairing effect on the HMT. These findings highlight the significant role of $np$ pairing and its interplay with SRCs in shaping nucleon momentum distributions in nuclear matter.

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arXiv2026

Complex-scaled no-core shell model calculations of bound and unbound nuclear states in light nuclei

The complex scaling method is commonly used to describe decaying states, but its applications are limited because the Hamiltonian operator must contain only relative coordinates. This has hindered the use of complex scaling in models defined with laboratory single-particle coordinates, and in particular one of the most important model in low-energy nuclear physics, the no-core shell model. We will then present a straightforward procedure for introducing complex scaling in the no-core shell model in order to calculate nuclear resonance states. For that matter, the complex-scaled two-body matrix elements must firstly be determined, and the resulting many-body Hamiltonian complex symmetric matrix must be diagonalized afterwards. Applications pertain to the bound ground states of the lightest nuclei $^2{\rm H}$, $^3{\rm H}$, $^3{\rm He}$, and $^4{\rm He}$, as well as the resonance ground states of $^5$He and $^5$Li, whereby the realistic interaction Daejeon16 is utilized.

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arXiv2019

Neutron-proton pairing in Nuclear Matter

The self-energy effect on the neutron-proton (np) pairing gap is investigated up to the third order within the framework of the extend Bruecker-Hartree-Fock (BHF) approach combined with the BCS theory. The self-energy up to the second-order contribution turns out to reduce strongly the effective energy gap, while the \emph{renormalization} term enhances it significantly. In addition, the effect of the three-body force on the np pairing gap is shown to be negligible. To connect the present results with the np pairing in finite nuclei, an effective density-dependent zero-range pairing force is established with the parameters calibrated to the microscopically calculated energy gap.

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