Precision study of the 14N(p, gamma)15O reaction at LUNA

The rate of the hydrogen-burning CNO cycle is controlled by the slowest reaction, 14N(p,gamma)15O. 15-30% of the total cross section are contributed by radiative capture to the ground state in 15O. Previous extrapolated S-factors for this ground state contribution disagree by a factor 2. The precision of those previous studies had been limited by a sizable true coincidence summing correction. In a new experiment using a segmented Clover detector deep underground at LUNA, the summing correction has been reduced by a factor 30, so existing R-matrix fits can now be precisely tested. The present data enable a direct measurement of the metallicity at the center of the Sun by detecting solar CNO neutrinos, for example at Borexino.