Coulomb Dissociation ofB8and the Low-Energy Cross Section of theBe7

Abstract

An exclusive measurement of the Coulomb breakup of 8 B into 7 Be+p at 254 A MeV allowed to study the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates and that E2 multipolarity can be neglected. By using a simple single-particle model for 8 B and treating the breakup in first-order perturbation theory, we extract a zero-energy S factor of S17(0) = 18.6 ± 1.2 ± 1.0 eV b, where the first error is experimental and the second one reflects the theoretical uncertainty in the extrapolation.

Precise measurement of theBe7(p,γ)B8Junghans1, Mohrmann2, Snover3 et al. 2003Phys. Rev. C141342794View full textAdd to dashboardCite

“…The good agreement between the S 17 (0) values determined from the 2 different fit ranges demonstrates that the energy dependence of the 7 Be(p,γ) 8 B cross section is wellunderstood and similar for all the direct experiments, and that the S 17 (0) value determined here is insensitive to the fit range. We show in Table VIII the best-fit DB results for S 17 (20), analogous to Table VII for S 17 (0).…”

“…[3]. He [43] argues that S 17 (20) should be used in solar model calculations, which avoids the need for derivatives since 20 keV is near the center of the Gamow window. Using S 17 (20) instead of S 17 (0) also avoids the need to extrapolate theoretical cross section calculations to zero energy.…”

“…For these reasons, we also quote our best-fit result for the S-factor at 20 keV: S 17 (20) = 21.4 ± 0.6(expt) ± 0.6(theor) eV b. (13) Table VI displays our S 17 (0) and S 17 (20) values obtained from the different theoretical extrapolations. There is a 3% variation in the ratio S 17 (20)/S 17 (0) among these theories, which is surprisingly large.…”

“…ies of the 7 Be(p,γ) 8 B cross section [4,5,6,7,8,9,10,11,12,13,14,15], and indirect studies using Coulombbreakup [16,17,18,19,20] or peripheral heavy-ion transfer and breakup [21,22] reactions. The direct technique has the advantage that it studies the reaction that actually occurs in the sun, but is difficult experimentally because it requires a radioactive target or beam, and the cross sections are small.…”

Photodissociation of neutron deficient nuclei

“…The validity of the CD approach has been recently demonstrated for the case of the 7 Be(p, γ) reaction, where very good agreement has been found between direct and indirect methods [23,24].…”