Astrophysical S-factor of the 14N(p,γ)15O reaction at 0.4 – 1.3MeV


Astrophysical S-factor of the 14N(p,γ)15O reaction at 0.4 – 1.3MeV

Wagner, L.; Akhmadaliev, S.; Anders, M.; Bemmerer, D.; Caciolli, A.; Gohl, S.; Grieger, M.; Junghans, A.; Marta, M.; Munnik, F.; Reinhardt, T. P.; Reinicke, S.; Röder, M.; Schmidt, K.; Schwengner, R.; Serfling, M.; Takács, M. P.; Szücs, T.; Vomiero, A.; Wagner, A.; Zuber, K.

The 14N(p,γ)15O 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 13N and 15O 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 15O, 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 15O, and at ten energies between 0.479-1.202 MeV for the second strongest transition, capture to the ground state in 15O. A simple R-matrix fit is performed to gauge the impact of the new data on astrophysical energies. The recently suggested slight enhancement of the ground state transition at low energy could not be confirmed. The present extrapolated zero-energy S-factors are S679(0) = 1.24±0.11 keVbarn and SGS(0) = 0.19±0.06 keVbarn.

Keywords: Nuclear Astrophysics; CNO cycle; Hydrogen burning

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