Astrophysical S-factor of the $^{14}\textrm{N(p,}\gamma\textrm{)}^{15}\textrm{O}$ reaction at 0.4 -- 1.3\,MeV

TL;DR

This study provides precise measurements of the astrophysical S-factor for the $^{14}$N(p,γ)$^{15}$O reaction over a range of energies, refining the reaction rate crucial for stellar models and solar neutrino predictions.

Contribution

It offers new, accurate S-factor data for key transitions in the reaction, reducing uncertainties and clarifying previous suggestions of low-energy enhancements.

Findings

Precise S-factor data at multiple energies for two transitions.

No confirmation of the previously suggested low-energy enhancement.

Updated zero-energy S-factors with reduced uncertainties.

Abstract

The $^{14}\textrm{N(p,}\gamma\textrm{)}^{15}\textrm{O}$ reaction is the slowest reaction of the carbon-nitrogen cycle of hydrogen burning and thus determines its rate. The precise knowledge of its rate is required to correctly model hydrogen burning in asymptotic giant branch stars. In addition, it is a necessary ingredient for a possible solution of the solar abundance problem by using the solar $^{13}$N and $^{15}$O neutrino fluxes as probes of the carbon and nitrogen abundances in the solar core. After the downward revision of its cross section due to a much lower contribution by one particular transition, capture to the ground state in $^{15}$O, the evaluated total uncertainty is still 8\%, in part due to an unsatisfactory knowledge of the excitation function over a wide energy range. The present work reports precise S-factor data at twelve energies between 0.357-1.292~MeV for the strongest transition, capture to the 6.79~MeV excited state in $^{15}$O, and at ten energies between 0.479-1.202~MeV for the second strongest transition, capture to the ground state in $^{15}$O. An R-matrix fit is performed to estimate the impact of the new data on astrophysical energies. The recently suggested slight enhancement of the 6.79~MeV transition at low energy could not be confirmed. The present extrapolated zero-energy S-factors are $S_{6.79}(0)$~=~1.24$\pm$0.11~keV~barn and $S_{\rm GS}(0)$~=~0.19$\pm$0.05~keV~barn.