Direct measurement of the14N(p, γ)15O S factor

The 14(p, γ)15O reaction regulates the rate of energy generation in the stellar CN cycle. Because discrepancies have been found in the analysis and interpretation of previous capture data, we have measured the 14N(p, γ)15O excitation function for energies in the range Eplab = 155-524 keV. Fits of these data using K-matrix theory yield a value for the S factor at zero energy of 1.68 ±0.09(stat) ± 0.16(syst) keVb, which is significantly smaller than the previous result. The corresponding reduction in the stellar reaction rate for 14N(p, γ)15O has a number of interesting consequences, including an impact on estimates for the age of the Galaxy derived from globular clusters