The Isospin Symmetry of the A=48, T=2 Mirror Nuclei Studied Through the Mirrored Knockout Technique

The study of excited states of mirror nuclei helps in the extraction of information pertaining to charge-dependent interactions between nucleons. An in-beam γ-ray spectroscopy experiment has been performed to establish a sequence of excited
states for the first time in the proton-rich nucleus (Tz=−2) 48Fe (Z = 26, N = 22) and to compare it with its well-known mirror nucleus (Tz = +2) 48Ti (Z = 22, N = 26) in the f7/2 shell.
The method of mirrored (i.e., analogue) one-nucleon knockout reactions was applied, in which the Tz = ±2 mirror pair, 48Fe/48Ti were populated via one-neutron/ one-proton knockout from the secondary beams 49Fe/49V, respectively. The new level scheme of 48Fe was established using the analogue properties of the reactions.
The inclusive and exclusive cross sections for knockout have been analyzed for the populated states and also compared with reaction model calculations. In the analysis, large differences between the cross sections of the two mirrored reactions
were observed and interpreted in terms of different degrees of binding of the mirror nuclei.
The mirror energy differences (MED) between the isobaric analogue T = 2 states of the 48Fe/48Ti have been determined and compared with large-scale shell-model calculations and interpreted in terms of isospin non-conserving (INC) effects. The present study demonstrates the importance of including all isospin-breaking terms to explain the experimental observations. The MED for this mirror pair A = 48, as a result of their location in the precise centre of an isolated f7/2 shell, are especially sensitive to excitations outside the f7/2 shell, and hence, they present a stringent test of the shell–model calculations.