R-matrix analysis of the 14N(p,γ)15O astrophysical S-factor Original Research Article

14N(p,γ)15O is the slowest reaction of the CNO cycle and thus it regulates stellar energy production, the flux of CNO neutrinos from the sun, and plays a role in determining the age of the globular clusters. We present R-matrix fits of the capture data to the ground state, the 6.79 MeV and the 6.18 MeV states in 15O from two recent and independent direct measurements of the 14N(p,γ)15O low-energy cross section, together with previous data. The results confirm that the rate of the 14N(p,γ)15O reaction is a factor of 2 lower than previously accepted for temperatures below 0.1 GK. The recommended astrophysical S-factor at zero energy is S(0)=1.70±0.07stat±0.10sys keV-barn. These results could increase the age at the main-sequence turnoff by about 0.5-1 Gy, provided that all other astrophysical parameters are known.