  The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is
controlled by the slowest process, 14N(p,gamma)15O, which proceeds by capture
to the ground and several excited states in 15O. 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.
