Speaker
Description
Isospin symmetry is a fundamental concept arising from the assumed charge symmetry and charge independence of the strong nuclear force. However, a wealth of experimental evidence has revealed isospin non-conserving interactions, which manifest, for example, in the excitation energies of analog states in $T$ = 1 triplet nuclei. Until recently, the triplet energy difference (TED) data were available for $A$ = 42 to $A$ = 74 isobaric triplets, but have now been extended to cover the $A$ = 78, $T$ = 1 triplet, which is currently the heaviest system for which complete TED data exist.
A fusion-evaporation reaction study conducted at the Accelerator Laboratory of the University of Jyvaskyla led to the first observation of the 2$^+$ and, tentatively, the 4$^+$ excited states in the $N$ = $Z$ - 2 nucleus $^{78}$Zr [1]. This study also provided new structural information for the $N$ = $Z$ nucleus $^{78}$Y. These results were obtained using the JUROGAM 3 Ge-array coupled with the vacuum-mode mass separator MARA, along with employing the recoil-$\beta$ and recoil-$\beta$-$\beta$ correlation techniques. This presentation will discuss the new experimental results for the $A$ = 78 triplet, which appear to be inconsistent with those obtained from contemporary theoretical calculations based on both the shell model and density functional theory.
References:
[1] G.L. Zimba, P. Ruotsalainen, D.G. Jenkins, W. Satula et al., Phys. Rev. Lett., Accepted 12 November, 2024
