Lifetime measurement of the 6.79 MeV state in [sup 15]O with the AGATA demonstrator

The N-14(p,gamma)O-15 reaction is the slowest process of the CN cycle, and thus it is of high astrophysical interest since it regulates the total rate of energy and neutrinos production through the cycle. The N-14+p ground state capture is strongly influenced by a sub-threshold resonance corresponding to the 6.79 MeV state in O-15. The width of this resonance is a major source of uncertainty in the extrapolation of the reaction cross section in the Gamow energy window. Preliminary results of a new Doppler Shift Attenuation measurement of the lifetime of the 6.79 MeV state in O-15 are discussed. The level of interest was populated via the H-2(N-14,n)O-15 reaction in inverse kinematics at 32 MeV beam energy. The gamma-rays emitted in the decay of the 6.79 MeV level to the ground state were detected with the AGATA Demonstrator array of high-purity germanium detectors. The sensitivity of the shape of the peak in the gamma-ray energy spectrum to the level lifetime is investigated comparing the experimental peaks with detailed Monte Carlo simulations of the reaction mechanisms and the gamma-ray emission and detection. Nuclear levels in N-15 (also populated in the N-14+H-2 reaction) for which the lifetimes are known in the literature provided a test of the analysis technique.