A new measurement of the proton capture rate on $^{7}$Be and the S$_{17}$(0) factor

The $^{7}$Be(p, $\gamma$) $ \,^{8}$B reaction plays a central role in the evaluation of solar neutrino fluxes. We report on a new precision measurement of the cross section of this reaction, following our previous experiment with an implanted target, a raster scanned beam and the elimination of back-scattering losses. The new measurement incorporates a higher activity $^{7}$Be target and a number of improvements in design and procedure. The cross section at Ec.m. = 850 keV was measured several times under varying experimental conditions, yielding a value of S$_{17}$(Ec.m.=850 keV) = 24.0 $\pm$ 0.5 eV b. Measurements were carried out at lower energies as well. We obtain from the entire set of measurements an extrapolated value of S$_{17}$(0) = 21.2 $\pm$ 0.7 eV b.