New astrophysicalSfactor for theN15(p,γ)O16reaction via the asymptotic normalization coefficient (ANC) method

Abstract

The ${}^{15}\mathrm{N}(p,\ensuremath{\gamma}){}^{16}\mathrm{O}$ reaction provides a path from the CN cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor for this reaction is dominated by resonant capture through two strong ${J}^{\ensuremath{\pi}}={1}^{\ensuremath{-}}$ resonances at ${E}_{R}=312$ and 962 keV and direct capture to the ground state. Asymptotic normalization coefficients (ANCs) for the ground and seven excited states in $^{16}\mathrm{O}$ were extracted from the comparison of experimental differential cross sections for the $^{15}\mathrm{N}$($^{3}\mathrm{He}$,$d)$$^{16}\mathrm{O}$ reaction with distorted-wave Born approximation calculations. Using these ANCs and proton and \ensuremath{\alpha} resonance widths determined from an $R$-matrix fit to the data from the ${}^{15}\mathrm{N}(p,\ensuremath{\alpha}){}^{12}\mathrm{C}$ reaction, we carried out an $R$-matrix calculation to obtain the astrophysical factor for the ${}^{15}\mathrm{N}(p,\ensuremath{\gamma}){}^{16}\mathrm{O}$ reaction. The results indicate that the direct capture contribution was previously overestimated. We find the astrophysical factor to be $S(0)=36.0\ifmmode\pm\else\textpm\fi{}6.0$ keV b, which is about a factor of 2 lower than the presently accepted value. We conclude that for every $2200\ifmmode\pm\else\textpm\fi{}300$ cycles of the main CN cycle one CN catalyst is lost due to this reaction.