Evolution of the Z=20 gap in neutron-rich Ca isotopes

In recent years, neutron-rich Ca isotopes have been studied extensively, both theoretically and experimentally, as this is a region where structure can have a dramatic influence on the location of the neutron dripline. Large-space ab-initio calculations based on NN+3N forces predict that the dripline could extend as far as $^{70}$Ca. However, recent data reveal deficiencies in theoretical predictions which reveal that extrapolating to the dripline may prove unreliable For example, an anomalously large charge radii was measured in $^{50,52}$Ca relative to $^{48}$Ca which challenges the doubly-magic nature of $^{52}$Ca. I will report on the results of an experiment performed at the NSCL with GRETINA to determine the proton single-particle occupancies using the (d,n) proton transfer reaction on $^{50}$Ca to states in $^{51}$Sc.