Lifetime measurement of the 6.79 MeV state in $15O$ with the AGATA demonstrator

The preliminary results of a new direct measurement of the lifetime of the first excited 3/2⁺ state in $15O$ are discussed. An accurate evaluation of this lifetime is of paramount importance for the determination of the cross section of the $14N(p,γ)15O$ reaction, the slowest one in the CNO cycle, at the energies of the solar Gamow peak. The $2H(14N,15O)n$ reaction in inverse kinematics at 32MeV beam energy (XTU Tandem, LNL) was used to populate the level of interest, which decays via a 6.79 MeV E1 gamma-ray transition to the ground state. Gamma rays were detected with 4 triple clusters of HPGe detectors of the AGATA Demonstrator array. The energy resolution and position sensitivity of this state-of-the-art gamma-ray spectrometer have been exploited to investigate the Doppler Shift Attenuation effect on the lineshape of the gamma-ray peak in the energy spectrum. The deconvolution of the lifetime effects from those due to the kinematics of the emitting nuclei has been performed using detailed Monte Carlo simulations of the gamma emission and detection. CDCC-CRC calculations for the nucleon transfer process have been used for this purpose and preliminary results are shown.