Halo structure of $^6$He from $\textit{ab initio}$ two-nucleon spatial correlations
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arXiv
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| Format: | Preprint |
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2025
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| author | Huang, Mengyao Frederico, Tobias Yin, Peng Basili, Robert A. M. Fasano, Patrick J. Vary, James P. |
| author_facet | Huang, Mengyao Frederico, Tobias Yin, Peng Basili, Robert A. M. Fasano, Patrick J. Vary, James P. |
| contents | We evaluate pairwise correlations using ground state wave functions for $^4$He and $^6$He obtained by $\textit{ab initio}$ no-core shell model (NCSM) calculations with the Daejeon16 nucleon-nucleon interaction plus Coulomb interaction, to characterize the structures of these two systems. We demonstrate that two-nucleon spatial correlations, specifically the pair-number operator $r^0$ and the square-separation operator $r^2$ projected on two-body spin $S$ and isospin $z$-components encode important details of the halo structure of $^6$He. We also analyze the single-particle state occupancies and the two-body state occupancies for the ground state of $^4$He and $^6$He. Our results indicate that the two valence neutrons in the ground state of $^6$He dominantly form a spin-singlet configuration. The rms pair separations between core nucleons and halo neutrons of $^6$He is about 80% larger than pair separations within the swollen and off-centered "$α$ core". We show that this off-centering effect is primarily responsible for the observed increase in point-proton radius $r_p$ in $^6$He relative to $^4$He. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_24123 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Halo structure of $^6$He from $\textit{ab initio}$ two-nucleon spatial correlations Huang, Mengyao Frederico, Tobias Yin, Peng Basili, Robert A. M. Fasano, Patrick J. Vary, James P. Nuclear Theory We evaluate pairwise correlations using ground state wave functions for $^4$He and $^6$He obtained by $\textit{ab initio}$ no-core shell model (NCSM) calculations with the Daejeon16 nucleon-nucleon interaction plus Coulomb interaction, to characterize the structures of these two systems. We demonstrate that two-nucleon spatial correlations, specifically the pair-number operator $r^0$ and the square-separation operator $r^2$ projected on two-body spin $S$ and isospin $z$-components encode important details of the halo structure of $^6$He. We also analyze the single-particle state occupancies and the two-body state occupancies for the ground state of $^4$He and $^6$He. Our results indicate that the two valence neutrons in the ground state of $^6$He dominantly form a spin-singlet configuration. The rms pair separations between core nucleons and halo neutrons of $^6$He is about 80% larger than pair separations within the swollen and off-centered "$α$ core". We show that this off-centering effect is primarily responsible for the observed increase in point-proton radius $r_p$ in $^6$He relative to $^4$He. |
| title | Halo structure of $^6$He from $\textit{ab initio}$ two-nucleon spatial correlations |
| topic | Nuclear Theory |
| url | https://arxiv.org/abs/2512.24123 |