Indirect methods have become the predominant approach in experimental nuclear astrophysics for studying several low-energy nuclear reactions occurring in stars, as direct measurements of many of these relevant reactions are rendered infeasible due to their low reaction probability. Such indirect methods, however, require theoretical input that in turn can have significant poorly quantified uncertainties, which can then be propagated to the reaction rates and have a large effect on our quantitative understanding of stellar evolution and nucleosynthesis processes. We present two such examples involving $\alpha$-induced reactions, ${}^{13}\mathrm{C}(\alpha ,n){}^{16}\mathrm{O}$ and ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$, for which the low-energy cross sections have been constrained with $({}^6\mathrm{Li},d)$ transfer data. In this Letter, we discuss how a first-principle calculation of ${}^6\mathrm{Li}$ leads to a 21% reduction of the ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ cross sections with respect to a previous estimation. This calculation further resolves the discrepancy between recent measurements of the ${}^{13}\mathrm{C}(\alpha ,n){}^{16}\mathrm{O}$ reaction and points to the need for improved theoretical formulations of nuclear reactions.

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• H & He burning
• Hydrostatic stellar nucleosynthesis
• Nuclear astrophysics
• Nuclear reactions
• Radiative capture
• S-factor
• s process