Baby L T, Bordeanu C, Goldring G, Hass M, Weissman L, Fedoseyev V N, Köster U, Nir-El Y, Haquin G, Gäggeler H W, Weinreich R
Department of Particle Physics, Weizmann Institute of Science, Rehovot, Israel.
Phys Rev Lett. 2003 Jan 17;90(2):022501. doi: 10.1103/PhysRevLett.90.022501. Epub 2003 Jan 15.
The 7Be(p,gamma)8B 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 7Be target, a raster-scanned beam, and the elimination of the backscattering loss. The new measurement incorporates a more abundant 7Be target and a number of improvements in design and procedure. The point at E(lab)=991 keV was measured several times under varying experimental conditions, yielding a value of S17(E(c.m.)=850 keV)=24.0+/-0.5 eV b. Measurements were carried out at lower energies as well. Because of the precise knowledge of the implanted 7Be 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 S17(0)=21.2+/-0.7 eV b.
7Be(p,γ)8B反应在太阳中微子通量评估中起着核心作用。继我们之前使用植入式7Be靶、光栅扫描束流并消除背散射损失的实验之后，我们报告了该反应截面的一项新的精确测量。新测量采用了丰度更高的7Be靶，并在设计和程序上有多项改进。在不同实验条件下对实验室能量E = 991 keV处的点进行了多次测量，得到S17（质心系能量E(c.m.) = 850 keV）= 24.0±0.5 eV·b的值。也在较低能量下进行了测量。由于对植入的7Be密度分布有精确了解，因此能够重构截面的非共振部分和共振部分，并从整套测量中获得S17(0) = 21.2±0.7 eV·b的外推值。
