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arXiv 2006.06305nucl-exastro-ph.SRnucl-th
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亚势垒能区${}^{12}$ C+ ${}^{12}$ C聚变反应的修正的天体物理S因子

The modified astrophysical S-factor of the ${}^{12}$C+${}^{12}$C fusion reaction at sub-barrier energies

Y. J. Li, X. Fang, B. Bucher, K. A. Li, L. H. Ru, X. D. Tang

摘要:

$^{12}$ C+ $^{12}$ C聚变反应在恒星演化和爆炸中起着至关重要的作用。其开放反应通道主要包括$α$、$p$、$n$和${}^{8}$ Be。尽管经过半个多世纪的努力,使用各种技术测量的实验数据之间仍然存在很大的差异。在这项工作中,我们使用统计模型分析现有的数据。我们的计算表明:2)$p$和$α$通道的总修正天体物理S因子(S $^*$因子)可以通过将其相应基态跃迁的S $^*$因子与特征$γ$射线相加而获得,同时考虑丢失通道对特征射线的贡献。应用校正后的统计模型预测的分支比的基础上,在${E}_{cm}>$ 4兆电子伏的不同的数据集之间达成协议,而一些差异仍然在较低的能量表明需要更好的测量在不久的将来。我们发现,最近的S $^*$因子从间接测量得到的是不一致的直接测量能量低于2.6 MeV。我们根据现有模型推荐${}^{12}$ C+ ${}^{12}$ C S $^*$因子的上限和下限。还建议采用新的$^{12}$ C+ $^{12}$ C反应速率。

英文摘要:

The $^{12}$C+$^{12}$C fusion reaction plays a crucial role in stellar evolution and explosions. Its open reaction channels mainly include $α$, $p$, $n$, and ${}^{8}$Be. Despite more than a half century of efforts, large discrepancies remain among the experimental data measured using various techniques. In this work, we analyze the existing data using the statistical model. Our calculation shows: 1) the relative systematic uncertainties of the predicted branching ratios get smaller as the predicted ratios increase; 2) the total modified astrophysical S-factors (S$^*$ factors) of the $p$ and $α$ channels can each be obtained by summing the S$^*$ factors of their corresponding ground-state transitions and the characteristic $γ$ rays while taking into account the contributions of the missing channels to the latter. After applying corrections based on branching ratios predicted by the statistical model, an agreement is achieved among the different data sets at ${E}_{cm}>$4 MeV, while some discrepancies remain at lower energies suggesting the need for better measurements in the near future. We find that the recent S$^*$ factor obtained from an indirect measurement is inconsistent with the direct measurement at energies below 2.6 MeV. We recommend upper and lower limits for the ${}^{12}$C+${}^{12}$C S$^*$ factor based on the existing models. A new $^{12}$C+$^{12}$C reaction rate is also recommended.

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