Many-channel microscopic cluster model of $^{8}$Be: S-factors
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| Format: | Preprint |
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2025
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| _version_ | 1866915647189942272 |
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| author | Zhaba, V. I. Lashko, Yu. A. Vasilevsky, V. S. |
| author_facet | Zhaba, V. I. Lashko, Yu. A. Vasilevsky, V. S. |
| contents | We investigate low--energy astrophysical $S$ factors for reactions proceeding through the $^{8}$Be compound system with entrance channels $p+{}^{7}$Li, $n+{}^{7}$Be, and $d+{}^{6}$Li. Using the same microscopic many--channel three--cluster framework as in our previous study of the high--lying $^{8}$Be spectrum, we calculate $S(E)$ for $^{7}$Li($p,α)^{4}$He, $^{7}$Be($n,α)^{4}$He, $^{7}$Be($n,p)^{7}$Li, $^{6}$Li($d,α)^{4}$He, $^{6}$Li($d,p)^{7}$Li, and $^{6}$Li($d,n)^{7}$Be in the energy range relevant for primordial and stellar nucleosynthesis. For the mirror pair $^{7}$Li($p,α)^{4}$He / $^{7}$Be($n,α)^{4}$He and for $^{7}$Be($n,p)^{7}$Li the calculated $S$ factors reproduce both the absolute scale and the low--energy trends of the experimental data within their quoted uncertainties, whereas the absolute $S$ factors for the deuteron--induced channels on $^{6}$Li are underestimated at low energy, consistent with the shifted $^{6}$Li+$d$ threshold and the absence of a broad subthreshold $2^{+}$ structure in the present implementation. A partial--wave analysis identifies the dominant $J^π$ contributions in each channel and relates them to specific $^{8}$Be resonances, while demonstrating that cluster polarization, previously shown to be crucial for the $^{8}$Be spectrum, is likewise essential for the normalization and energy dependence of several $S$ factors. Evaluating $S(E)$ at appropriate Gamow energies, we obtain a hierarchy of reaction channels that quantifies the relative importance of neutron-- and deuteron--induced processes for the production and destruction of $^{7}$Li and $^{7}$Be. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_01846 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Many-channel microscopic cluster model of $^{8}$Be: S-factors Zhaba, V. I. Lashko, Yu. A. Vasilevsky, V. S. Nuclear Theory We investigate low--energy astrophysical $S$ factors for reactions proceeding through the $^{8}$Be compound system with entrance channels $p+{}^{7}$Li, $n+{}^{7}$Be, and $d+{}^{6}$Li. Using the same microscopic many--channel three--cluster framework as in our previous study of the high--lying $^{8}$Be spectrum, we calculate $S(E)$ for $^{7}$Li($p,α)^{4}$He, $^{7}$Be($n,α)^{4}$He, $^{7}$Be($n,p)^{7}$Li, $^{6}$Li($d,α)^{4}$He, $^{6}$Li($d,p)^{7}$Li, and $^{6}$Li($d,n)^{7}$Be in the energy range relevant for primordial and stellar nucleosynthesis. For the mirror pair $^{7}$Li($p,α)^{4}$He / $^{7}$Be($n,α)^{4}$He and for $^{7}$Be($n,p)^{7}$Li the calculated $S$ factors reproduce both the absolute scale and the low--energy trends of the experimental data within their quoted uncertainties, whereas the absolute $S$ factors for the deuteron--induced channels on $^{6}$Li are underestimated at low energy, consistent with the shifted $^{6}$Li+$d$ threshold and the absence of a broad subthreshold $2^{+}$ structure in the present implementation. A partial--wave analysis identifies the dominant $J^π$ contributions in each channel and relates them to specific $^{8}$Be resonances, while demonstrating that cluster polarization, previously shown to be crucial for the $^{8}$Be spectrum, is likewise essential for the normalization and energy dependence of several $S$ factors. Evaluating $S(E)$ at appropriate Gamow energies, we obtain a hierarchy of reaction channels that quantifies the relative importance of neutron-- and deuteron--induced processes for the production and destruction of $^{7}$Li and $^{7}$Be. |
| title | Many-channel microscopic cluster model of $^{8}$Be: S-factors |
| topic | Nuclear Theory |
| url | https://arxiv.org/abs/2512.01846 |