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

The $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ 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 $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ excitation function for energies in the range ${E}_{p}^{\mathrm{l}\mathrm{a}\mathrm{b}}=155--524\text{ }\text{ }\mathrm{k}\mathrm{e}\mathrm{V}$. Fits of these data using $R$-matrix theory yield a value for the $S$ factor at zero energy of $1.68\ifmmode\pm\else\textpm\fi{}0.09(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.16(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\text{ }\text{ }\mathrm{k}\mathrm{e}\mathrm{V}\text{ }\mathrm{b}$, which is significantly smaller than the previous result. The corresponding reduction in the stellar reaction rate for $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ has a number of interesting consequences, including an impact on estimates for the age of the Galaxy derived from globular clusters.