Asymptotic normalization coefficients for14N+P→15O and the14N(P,γ)15O astrophysical S factors at extremely low energies

Full text: In the present work, the results of the reanalysis of the experimental astrophysical S factors Sexp(E) for the 14N(p, γ )15O reactions [1] reactions at extremely low energies are presented. The analysis is performed within the R-matrix method in which the new information about the values of the asymptotic normalization constants (ANC) of the overlap function for the bound wave functions of the residual nucleus in the (16N+p)- channel (or respective the nuclear vertex constant for the virtual decay 15O →14N+p ) are used to fix the direct part amplitude. The ANC- values, which were obtained in [2] from the DWBA - analysis of the 14N(3He,d)15O reaction populating to the ground and excited (6.18 , 6.79 and 6.86 MeV) states, are used. We fit values of the resonance parameters (the radiative width Γγ and the proton width Γp ) corresponding to the resonance ( E* =7.556 MeV) states for transition to the excited (6.790 and 6.859 MeV) and the several higher lying resonance states for transition to the ground and excited (6.18 MeV) states. To obtain a reasonable fit to the experimental data, a contribution from a background pole generated by distant resonances must be taken into account. The new estimation for these resonance parameters is obtained. We find that the astrophysical S factor for the capture to the ground state is S(0) =0.27 keV b. The capture to the third excited (6.18 MeV) state contributes from direct capture and resonance captures through the first, second, subthreshold and background resonances. The found S(0) astrophysical S factor for the third excited state is S(0)=0.15 keV. The capture to subthreshold (6.79 MeV) has contributions from resonance capture through the first resonance and direct E1 capture. The calculated S(0) astrophysical factor for the subthreshold state is S(0) =1.26 keV b. The capture to the excited (6.859 MeV) state has from contribution only from direct capture and the corresponding S(0) astrophysical S factor is S(0)=0.04 keV b. The total calculated astrophysical S factor at zero energy is S(0)=1.72 keV. Also, comparison of our results with those obtained other authors is done. References: 1. U. Schroder et al. Nucl.Phys. A 467 (1987) 240; 2. S.V. Artemov et al. Phys.At.Nucl. 67(1996)428 (authors)