Asymptotic normalization coefficients (nuclear vertex constants) for p + 7Be → 8B and the direct 7Be(p, γ)8B astrophysical S factors at solar energies
Abstract
A new analysis of the precise experimental astrophysical S factors for the direct-capture reaction 7Be(p, γ)8B [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 + 7Be → 8B 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 + 7Be)-state wave function and for p 7Be-scattering wave function. New estimates are obtained for the “indirectly measured” values of the asymptotic normalization constants (the nuclear vertex constants) for the p + 7Be → 8B 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 7Be scattering.