Search

We present S factor data obtained from the Coulomb dissociation of 83 MeV/nucleon B-8, and analyze Be-7 longitudinal momentum distributions measured at 44 and 81 MeV/nucleon using a potential model, first-order perturbation theory, and dynamical solution of the time-dependent Schrodinger equation. Comparing our results with independent continuum-discretized coupled channels calculations, we study the reaction model and beam energy dependence of the E2 contribution to the dissociation cross section. By fitting radiative capture and Coulomb breakup data taken below relative energies of 400 keV with potential models constrained by Li-7+n and Be-7+p elastic scattering data, we examine the mutual consistency of recent S-17 measurements and obtain a recommended value for S-17(0) of 18.6+/-0.4 (experimental) +/-1.1 (extrapolation) eV b (1sigma). This result is in good agreement with recent experimental determinations of the asymptotic normalization coefficient of the valence proton wave function in B-8.

We present S factor data obtained from the Coulomb dissociation of 83 MeV/nucleon B-8, and analyze Be-7 longitudinal momentum distributions measured at 44 and 81 MeV/nucleon using a potential model, first-order perturbation theory, and dynamical solution of the time-dependent Schrodinger equation. Comparing our results with independent continuum-discretized coupled channels calculations, we study the reaction model and beam energy dependence of the E2 contribution to the dissociation cross section. By fitting radiative capture and Coulomb breakup data taken below relative energies of 400 keV with potential models constrained by Li-7+n and Be-7+p elastic scattering data, we examine the mutual consistency of recent S-17 measurements and obtain a recommended value for S-17(0) of 18.6+/-0.4 (experimental) +/-1.1 (extrapolation) eV b (1sigma). This result is in good agreement with recent experimental determinations of the asymptotic normalization coefficient of the valence proton wave function in B-8.

In an effort to better determine the Be-7(p, gamma)B-8 reaction rate, we have performed inclusive and exclusive measurements of the Coulomb dissociation of B-8. The former was a study of longitudinal momentum distributions of Be-7 fragments emitted in the Coulomb breakup of intermediate energy B-8 beams on Pb and Ag targets. Analysis of these data yielded the E2 contribution to the breakup cross section. In the exclusive measurement. we determined the cross section for the Coulomb breakup of B-8 on Pb at low relative energies in order to infer the astrophysical S factor for the Be-7(p, gamma)B-8 reaction. Interpreting the measurements with first-order perturbation theory, we obtained S-E2/S-E1 = 4.7(-1.3)(+2.0) x 10(-4) at E-rel = 0.6 MeV, and S-17(0) =17.8(-1.2)(+1.4) eV b. Semiclassical first-order perturbation theory and fully quantum mechanical continuum-discretized coupled channels analyses yield nearly identical results for the El strength relevant to solar neutrino flux calculations, suggesting that theoretical reaction mechanism uncertainties need not limit the precision of Coulomb breakup determinations of the Be-7(p, gamma)B-8 S factor. A recommended value of S-17(0) based on a weighted average of this and other measurements is presented.

In an effort to better determine the Be-7(p, gamma)B-8 reaction rate, we have performed inclusive and exclusive measurements of the Coulomb dissociation of B-8. The former was a study of longitudinal momentum distributions of Be-7 fragments emitted in the Coulomb breakup of intermediate energy B-8 beams on Pb and Ag targets. Analysis of these data yielded the E2 contribution to the breakup cross section. In the exclusive measurement. we determined the cross section for the Coulomb breakup of B-8 on Pb at low relative energies in order to infer the astrophysical S factor for the Be-7(p, gamma)B-8 reaction. Interpreting the measurements with first-order perturbation theory, we obtained S-E2/S-E1 = 4.7(-1.3)(+2.0) x 10(-4) at E-rel = 0.6 MeV, and S-17(0) =17.8(-1.2)(+1.4) eV b. Semiclassical first-order perturbation theory and fully quantum mechanical continuum-discretized coupled channels analyses yield nearly identical results for the El strength relevant to solar neutrino flux calculations, suggesting that theoretical reaction mechanism uncertainties need not limit the precision of Coulomb breakup determinations of the Be-7(p, gamma)B-8 S factor. A recommended value of S-17(0) based on a weighted average of this and other measurements is presented.