$^7$Be($p,\gamma$)$^8$B S-factor from {\it ab initio} wave functions: II. S-factor calculation

The S-factors ($S_{17}$ for the radiative capture reaction p+$^7 $Be$\rightarrow ^8$B+$\gamma$ are calculated using {\it ab initio} no-core shell model (NCSM) overlap integrals with corrected asymptotics. Momentum distributions for the reactions $^8$B (41 MeV/nucleon) + $^9$Be$\rightarrow ^7$Be+X and $^8$B (936 MeV/nucleon) + $^{12}$C$\rightarrow ^7$Be+X have also been studied. A good description of both the experimental data of both the astrophysical S-factor and of the momentum distributions over a wide energy/momentum spectrum is obtained. The spectroscopic factors obtained with the NCSM wavefunctions are also shown to be in good agreement with the experimental data. Our studies support a value of $S_{17}$ in agreement with recent Coulomb dissociation experiments, but which are slightly below the averaged values from direct capture experiments [1]. [1] W.C. Haxton, P.D. Parker, C.E. Rolfs, archive preprint nucl- th/0501020.