The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is controlled by the slowest process, ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$, which proceeds by capture to the ground and several excited states in ${}^{15}\mathrm{O}$. Previous extrapolations for the ground state contribution disagreed by a factor 2, corresponding to 15% uncertainty in the total astrophysical $S$ factor. At the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy, a new experiment on ground state capture has been carried out at 317.8, 334.4, and 353.3 keV center-of-mass energy. Systematic corrections have been reduced considerably with respect to previous studies by using a Clover detector and by adopting a relative analysis. The previous discrepancy has been resolved, and ground state capture no longer dominates the uncertainty of the total $S$ factor.

• Received 10 April 2008

DOI:https://doi.org/10.1103/PhysRevC.78.022802