Shell structure study on ⁴³S via one-neutron knockout reaction

South of ⁴⁸Ca in the nuclear chart, the erosion of the neutron magic number 28 has been observed.
Especially the ground-state deformation, the shape coexistence, and the high-K isomerism in ⁴⁴S have been discussed both experimentally and theoretically.
These phenomena are thought to originate from the interplay of quenching the N = 28 shell gap and quadrupole excitations across Z = 14, 16 sub-shell and N = 28 shell gaps.
To clarify the reduction of the N = 28 shell gap and the role of the neutron configuration to the deformation in ⁴⁴S, an in-beam γ-ray spectroscopic study focused on the one-neutron knockout reaction from ⁴⁴S was performed.

The experiment was performed at the NSCL.
Prompt γ-rays from excited states in ⁴³S were detected by the GRETINA tracking array.
In order to construct the level scheme above the isomeric state at 320 keV in ⁴³S and population to this state for the deduction of the neutron configuration in the fp shell, the IsoTagger which consists of 32 CsI scintillators was placed  downstream at the end of the beam line.

The level scheme and production cross section of each state of ⁴³S, combined with the analysis on momentum distributions produced by this reaction, will be discussed by comparing with some shell model calculations.