Low-energy cross section of theBe7(p,γ)B8solar fusion reaction from the Coulomb dissociation ofB8

Abstract

An exclusive measurement of the Coulomb breakup of {sup 8}B into {sup 7}Be+p at 254A MeV was used to infer the low-energy {sup 7}Be(p,{gamma}){sup 8}B cross section. The radioactive {sup 8}B beam was produced by projectile fragmentation of 350A MeV {sup 12}C and separated with the FRagment Separator (FRS) at Gesellschaft fuer Schwerionenforschung 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 S{sub 17} factors exhibit good agreement with the most recent direct {sup 7}Be(p,{gamma}){sup 8}B measurements. By using the energy dependence of S{sub 17} according to the recently refined cluster model for {sup 8}B of P. Descouvemont [Phys. Rev. C 70, 065802 (2004)], we extract a zero-energy S factor of S{sub 17}(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 by Descouvemont to be about 5%.