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

14 N(p, γ ) 15 O 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 15 O from two recent and independent direct measurements of the 14 N(p, γ ) 15 O low-energy cross section, together with previous data. The results confirm that the rate of the 14 N(p, γ ) 15 O 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 ± 0.07 s t a t ± 0.10 s y s 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.