Ground State Wave Function of $^{12}$Be

Spectroscopic factors are important quantities in establishing the shell structure in nuclei. We measured the spectroscopic factor for the neutron knockout reaction of a $^{12}$Be beam into the neutron unbound d$_{5/2}$ state of $^{11}$Be using neutron-fragment coincidence measurements. The secondary $^{12}$Be beam was produced from a 120 MeV/nucleon $^{18}$O beam from the Coupled Cyclotron Facility at the NSCL. The $^{10}$Be fragments were detected and identified using the MSU/FSU sweeper magnet while the neutrons were detected by the Modular Neutron Array (MoNA). From the reconstructed invariant mass spectra the relative contributions from different states in $^{11}$Be can be extracted.