We report on a new measurement of the 14N(p,γ) 15O capture cross section at Ep=140 to 400 keV using the 400 kV LUNA accelerator facility at the Laboratori Nazionali del Gran Sasso (LNGS). The uncertainties have been reduced with respect to previous measurements and their analysis. We have analyzed the data using the R-matrix method and we find that the ground state transition accounts for about 15% of the total S-factor. The main contribution to the S-factor is given by the transition to the 6.79 MeV state. We find a total S(0)=1.7±0.2 keVb, in agreement with recent extrapolations. The result has important consequences for the solar neutrino spectrum as well as for the age of globular clusters. © 2004 Elsevier B.V. All rights reserved.info:eu-repo/semantics/publishe

We give the LUNA results on the $\sigma \left(E\right)$ cross section measurement of a key reaction of the proton-proton chain strongly affecting the calculated neutrino luminosity from the Sun: ${}^3\mathrm{He}{(}^3\mathrm{He},2p{)}^4\mathrm{He}$. Because of the cosmic ray suppression provided by the Gran Sasso underground laboratory, it has been possible to measure $\sigma \left(E\right)$ throughout the energy range in which this reaction occurs in the Sun, i.e., down to $16.5\mathrm{keV}$ center of mass energy. The data clearly show the cross section increase due to the electron screening effect but they do not exhibit any evidence for a narrow resonance suggested to explain the ${}^8\mathrm{B}$ and ${}^7\mathrm{Be}$ solar neutrino flux reduction.