New measurement of the proton capture rate on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow/><mml:mrow><mml:mn>7</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Be</mml:mi></mml:math>and the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>S</mml:mi></mml:mrow><mml:mrow><mml:mn>17</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mn/><mml:mo>(</mml:mo><mml:mn>0</mml:mn><mml:mo>)</mml:mo><mml:mn/></mml:math>factor

The ${}^{7}\mathrm{Be}(p,\ensuremath{\gamma}{)}^{8}\mathrm{B}$ 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 ${}^{7}\mathrm{Be}$ target, a raster-scanned beam, and the elimination of backscattering losses. The new measurement incorporates a higher activity ${}^{7}\mathrm{Be}$ target and a number of improvements in design and procedure. The cross section at a selected energy ${E}_{\mathrm{c}.\mathrm{m}.}=850\mathrm{keV}$ (where c.m. stands for center of mass) was measured several times under varying experimental conditions, yielding a value of ${S}_{17}{(E}_{\mathrm{c}.\mathrm{m}.}=850\mathrm{keV})=24.0\ifmmode\pm\else\textpm\fi{}0.5\mathrm{eV}\mathrm{}\mathrm{b},$ to serve as a benchmark. Measurements were carried out at lower energies as well. Due to the precise knowledge of the implanted ${}^{7}\mathrm{Be}$ density profile, it was possible to reconstitute both the off- and on-resonance parts of the cross section and to obtain from the entire set of measurements an extrapolated value of ${S}_{17}(0)=21.2\ifmmode\pm\else\textpm\fi{}0.7\mathrm{eV}\mathrm{}\mathrm{b},$ using the cluster model of Descouvemont and Baye.

Перевод пока недоступен