O – the source of the solar CNO neutrino flux *

BOREXINO has recently measured for the first time the flux of neutrinos from the decay of radioactive ¹⁵O in the solar core, providing a unique and direct way to determine the solar metallicity. The CNO neutrino flux depends directly on the solar ¹⁵O abundance, which in turn is determined by the ¹⁴N(p,γ)¹⁵O reaction rate at solar temperatures. This reaction rate relies largely on the extrapolation of the experimentally obtained reaction cross section data towards solar energies. This extrapolation carries significant uncertainties due to the complex interference patterns near the particle threshold in ¹⁵O, which in turn  translates into a substantial uncertainty for a reliable prediction of the solar metallicity. We will present new data on low energy measurements at the CASPAR underground accelerator laboratory and lifetime measurements of ¹⁵O threshold states at the Nuclear Science Laboratory at Notre Dame to yield a much  improved prediction for the reaction rate at solar temperatures and therefore a more reliable prediction for the solar metallicity to be compared with the BOREXINO data.