Knockout Reactions from $p$-Shell Nuclei: Tests of Ab Initio Structure Models

Absolute cross sections have been determined following single neutron knockout reactions from ${}^{10}\mathrm{Be}$ and ${}^{10}\mathrm{C}$ at intermediate energy. Nucleon density distributions and bound-state wave function overlaps obtained from both variational Monte Carlo (VMC) and no core shell model (NCSM) ab initio calculations have been incorporated into the theoretical description of knockout reactions. Comparison to experimental cross sections demonstrates that the VMC approach, with the inclusion of 3-body forces, provides the best overall agreement while the NCSM and conventional shell-model calculations both overpredict the cross sections by 20% to 30% for ${}^{10}\mathrm{Be}$ and by 40% to 50% for ${}^{10}\mathrm{C}$, respectively. This study gains new insight into the importance of 3-body forces and continuum effects in light nuclei and provides a sensitive technique to assess the accuracy of ab initio calculations for describing these effects.

Figure 1

Longitudinal momentum distributions for ${}^9\mathrm{Be}$ (top) and ${}^9\mathrm{C}$ (bottom) reaction residues constructed from four overlapping magnetic rigidities. An eikonal-plus-Gaussian fit was employed to estimate the unobserved cross section in the low and high momentum tails.

Figure 2

Bound-state VMC and NCSM wave function overlaps and resulting fits that use a Woods-Saxon-plus-spin-orbit potential. (Inset) Integrals of the square overlaps that saturate at the theoretical spectroscopic factor.