Precise measurement of theBe7(p,γ)B8Sfactor

We present new measurements of the ${}^7\mathrm{Be}\left(p,\gamma \right){}^8\mathrm{B}$ cross section from ${\overline{E}}_{\text{c.m.}}=116$ to $2460\text{keV}$ (where c.m. means center-of-mass), which incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to $S_{17}\left(0\right)=22.1\pm 0.6\left(\exp \mathrm{t}\right)\pm 0.6\left(\text{theor}\right)\text{eV}\mathrm{b}$ based on data from ${\overline{E}}_{\text{c.m.}}=116$ to $362\text{keV}$, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low-energy data. We compare our results to other $S_{17}\left(0\right)$ values extracted from both direct $\left[{}^7\mathrm{Be}\left(p,\gamma \right){}^8\mathrm{B}\right]$ and indirect (Coulomb-dissociation and heavy-ion reaction) measurements, and show that the results of these three types of experiments are not mutually compatible. We recommend a “best” value, $S_{17}\left(0\right)=21.4\pm 0.5\left(\exp \mathrm{t}\right)\pm 0.6\left(\text{theor}\right)\text{eV}\mathrm{b}$, based on the mean of all modern direct measurements below the $1^{+}$ resonance. We also present $S$ factors at $20\text{keV}$ which is near the center of the Gamow window: the result of our measurements is $S_{17}\left(20\right)=21.4\pm 0.6\left(\exp \mathrm{t}\right)\pm 0.6\left(\text{theor}\right)\text{eV}\mathrm{b}$, and the recommended value is $S_{17}\left(20\right)=20.6\pm 0.5\left(\exp \mathrm{t}\right)\pm 0.6\left(\text{theor}\right)\text{eV}\mathrm{b}$.