Scattering of ${}^7\mathrm{Be}$ and ${}^8\mathrm{B}$ and the astrophysical ${\text{S}}_{17}$ 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 ${}^8\mathrm{B}$ → ${}^7\mathrm{Be}+p$. The new value, $C_{\mathrm{tot}}^2({}^{8}B)=0.466\pm 0.049$ fm${}^{-1}$, is slightly larger than, but consistent with, the previous result. This implies an astrophysical factor, $S_{17}(0)=18.0\pm 1.9$ eV b, for the solar neutrino-generating reaction ${}^7\mathrm{Be}$($p,\gamma$)${}^8\mathrm{B}$.

Figure 1

(Color online) A three-dimensional view of the detector assembly.

Figure 2

(Color online) Angular distribution for elastic scattering of ${}^7\mathrm{Be}$ on ${}^{14}\mathrm{N}$ and ${}^{12}\mathrm{C}$. The points are experimental data after subtraction of the inelastic-scattering contribution. The solid (red) curve is the new calculation labeled E in Table , and the dashed curve (blue) is the previous calculation from Ref. 12. Both calculations are smeared to account for finite angular resolution.

Figure 3

(Color online) The angular distribution for elastic scattering of ${}^8\mathrm{B}$ on C. The dashed curve is the calculated cross section, and the solid curve is the result after the finite angular resolution is accounted for.