Knockout fromAr46:ℓ=3neutron removal and deviations from eikonal theory

The $^{9}\mathrm{Be}(^{46}\mathrm{Ar},^{45}\mathrm{Ar}+\ensuremath{\gamma})X$ one-neutron removal reaction has been studied in inverse kinematics at 70 MeV/nucleon. Coincidences with \ensuremath{\gamma} rays served to disentangle knockout events leading to the $^{45}\mathrm{Ar}$ ground state. The measured partial cross section corresponds to a spectroscopic factor of 4.9(7). The residue momentum distribution is compared with new calculations based on eikonal theory and represents the first case of an $\ensuremath{\ell}=3$ neutron removal, as is expected for populating a $0{f}_{7/2}$ hole in the $N=28$ projectile. However, the measured $^{45}\mathrm{Ar}$ momentum distribution has a marked low-momentum tail suggestive of dissipative effects whereas the eikonal model predictions are symmetric. The angular distribution of the residues confirms that there is a deviation from the model.