Precise nuclear data of the 14N(p,γ)15O reaction for solar neutrino predictions

The 14N(p,γ)15O reaction is the slowest stage of the carbon-nitrogen-oxygen cycle of hydrogen burning and thus determines its reaction rate. Precise knowledge of its rate is required to improve the model of hydrogen burning in our sun. The reaction rate is a necessary ingredient for a possible solution of the solar abundance problem that led to discrepancies between predictions of the solar standard model and helioseismology. The solar 13N and 15O neutrino fluxes are used as independent observables that probe the carbon and nitrogen abundances in the solar core. This could settle the disagreement, if the 14N(p,γ)15O reaction rate is known with high precision. After a review of several measurements its cross section was revised downward due to a much lower contribution by one particular transition, capture to the ground state in 15O. The evaluated total relative uncertainty is still 7.5%, in part due to an unsatisfactory knowledge of the excitation function over a wide energy range.
The present work reports experimentally determined cross sections as astrophysical S- factor data at twelve energies between 0.357 – 1.292 MeV for the strongest transition, capture to the 6.79MeV excited state in 15O with lower uncertainties than before and at ten energies between 0.479 – 1.202 MeV for the second strongest transition, capture to the ground state in 15O.
In addition, an R-matrix fit is performed to estimate the impact of the new data on the astrophysical relevant energy range. The recently suggested slight S-factor enhancement at the Gamow window could not be confirmed and differences to previous measurements at energies around 1 MeV were observed. The present extrapolated zero-energy S-factors are S679(0) = (1.19±0.10) keV b and SGS(0) = (0.25±0.05) keV b and they are within the uncertainties consistent with values recommended by the latest review.