Beta decay of the exotic $T_z$ = -2 nuclei $^{48}$Fe, $^{52}$Ni and $^{56}$Zn

The results of a study of the beta decays of three proton-rich nuclei with $T_z=\text{-}2$, namely $^{48}$Fe, $^{52}$Ni and $^{56}$Zn, produced in an experiment carried out at GANIL, are reported. In all three cases we have extracted the half-lives and the total $β$-delayed proton emission branching ratios. We have measured the individual $β$-delayed protons and $β$-delayed $γ$ rays and the branching ratios of the corresponding levels. Decay schemes have been determined for the three nuclei, and new energy levels are identified in the daughter nuclei. Competition between $β$-delayed protons and $γ$ rays is observed in the de-excitation of the $T=2$ Isobaric Analogue States in all three cases. Absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. In addition, we discuss in detail the data analysis taking as a test case $^{56}$Zn, where the exotic $β$-delayed $γ$-proton decay has been observed.