Asymptotic Normalization Coefficients (Nuclear Vertex Constants) for p + 7Be → 8B and the Direct 7Be(p, γ)8B Astrophysical S Factors at Solar Energies

A new analysis of the precise experimental astrophysical S factors for the direct-capture reaction Be-7(p, gamma)B-8 [A.J. Junghans et al., Phys. Rev. C 68, 065803 (2003) and L.T. Baby et al., Phys. Rev. C 67, 065805 (2003)] is carried Out On the basis of a modified two-body potential approach in which the direct astrophysical S factor, S-17(E), is expressed in terms of the asymptotic normalization constants for p + Be-7 --> B-8 and two additional conditions are involved to verify the peripheral character of the reaction under consideration. The Woods-Saxon potential form is used for the bound-(p + Be-7)-state wave function and for p(7)Be-scattering wave function. New estimates are obtained for the Indirectly measured values of the asymptotic normalization constants (the nuclear vertex constants) for the p + Be-7 --> B-8 and S-17(E) at E <= 115 keV, including E = 0. These Values of S-17(E) and asymptotic normalization constants have been used for obtaining the indirectly measured values of the s-wave average scattering length and the p-wave effective-range parameters for p(7)Be scattering.