Scattering of Be-7 and B-8 and the astrophysical S(17) factor

Measurements of $^{7}\mathrm{Be}$ scattering at 87 MeV on a melamine (${\text{C}}_{3}{N}_{6}{H}_{6}$) target and of $^{8}\mathrm{B}$ at 95 MeV on C were performed. For $^{7}\mathrm{Be}$ the angular range was extended over previous measurements and monitoring of the intensity of the radioactive beam was improved. The measurements provide a renormalization of the absolute cross section of existing data on the proton transfer reaction $^{14}\mathrm{N}$($^{7}\mathrm{Be}$,$^{8}\mathrm{B}$)$^{13}\mathrm{C}$ and lead to improved optical-model potentials used in the incoming and outgoing channels for the distorted-wave Born approximation analysis. The results yield an updated determination of the asymptotic normalization coefficient for the virtual decay $^{8}\mathrm{B}$ \ensuremath{\rightarrow} $^{7}\mathrm{Be}+p$. The new value, ${C}_{\mathrm{tot}}^{2}({}^{8}B)=0.466\ifmmode\pm\else\textpm\fi{}0.049$ fm${}^{\ensuremath{-}1}$, is slightly larger than, but consistent with, the previous result. This implies an astrophysical factor, ${S}_{17}(0)=18.0\ifmmode\pm\else\textpm\fi{}1.9$ eV b, for the solar neutrino-generating reaction $^{7}\mathrm{Be}$($p,\ensuremath{\gamma}$)$^{8}\mathrm{B}$.