Low-energy cross section of theBe7(p,γ)

Abstract

An exclusive measurement of the Coulomb breakup of 8 B into 7 Be+p at 254 A MeV was used to infer the low-energy 7 Be(p,γ) 8 B cross section. The radioactive 8 B beam was produced by projectile fragmentation of 350 A MeV 12 C and separated with the fragment separator FRS at GSI in Darmstadt, Germany. The Coulomb-breakup products were momentum-analyzed in the KaoS magnetic spectrometer; particular emphasis was placed on the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates within the angular cuts selected for the analysis. The deduced astrophysical S17 factors exhibit good agreement with the most recent direct 7 Be(p,γ) 8 B measurements. By using the energy dependence of S17 according to the recently refined cluster model for 8 B of Descouvemont, we extract a zero-energy S factor of S17(0) = 20.6 ± 0.8(stat) ± 1.2(syst) eV b. These errors do not include the uncertainty of the theoretical model to extrapolate to zero relative energy, estimated to be about 5% by Descouvemont.

From nucleons to nuclei to fusion reactions

“…The resulting S 17 astrophysical factor is compared to several experimental data sets in Figure 8. Energy dependence and absolute magnitude follow closely the trend of the indirect Coulomb breakup measurements of Shümann et al [56,57], while somewhat underestimating the direct data of Junghans et al [58]. The resonance, particularly evident in these and Filippone's data, is due to the M 1 capture, which does not contribute to a theoretical calculation outside of the narrow 8 B 1 + resonance and is negligible at astrophysical energies [59,60].…”

Combiningab initiocalculations and low-energy effective field theory for halo nuclear systems: The case ofBe7+p→B8Zhang1, Nollett2, Phillips3 2014Phys. Rev. C400260View full textAdd to dashboardCite

“…In contrast, the impact of scattering length uncertainties increases dramatically with energy: when E < 0.1 MeV, it is < 5%, but it reaches 20% at E ≈ 0.4 MeV. The consequent range of Halo-EFT predictions is consistent with direct capture data for 0.1 ≤ E ≤ 0.4 MeV (below the M 1 resonance) and with indirect S-factors derived from Coulomb breakup [35][36][37]. However, the energy dependence seen at the upper edge of the band in Fig.…”

Nuclear astrophysics with radioactive beams

“…The first experiment used a 199 mg/cm 2 208 Pb target, the second experiment used a Pb target of 50 mg/cm 2 thickness. Tracking of the angle of the incoming beam with parallel-plate avalanche counters allowed one to measure angular distributions to disentangle contributing multipolarities in the second experiment [38,337].…”