Knockout from 46Ar:ℓ=3 neutron removal and deviations from eikonal theory

The ⁹Be(⁴⁶Ar,⁴⁵Ar+γ)X one-neutron removal reaction has been studied in inverse kinematics at 70 MeV/nucleon. Coincidences with γ rays served to disentangle knockout events leading to the ⁴⁵Ar 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 ℓ=3 neutron removal, as is expected for populating a 0f_7/2 hole in the N=28 projectile. However, the measured ⁴⁵Ar 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.