Mass of self-conjugate nucleus ⁸⁰Zr reveals a deformed double shell closure at N=Z=40

The neutron-deficient region around ⁸⁰Zr is an area of great interest for nuclear structure due to the rapid change in nuclear shape with proton and neutron numbers. For the self-conjugate ⁸⁰Zr nucleus, spherical and deformed structures are expected to coexist at low energies, and their competition strongly depends on the size of the calculated N=Z=40 gap. In addition to shape-coexistence effects, ⁸⁰Zr offers a venue to study the Wigner energy reflecting an additional binding in self-conjugate nuclei and their neighbors. Mass differences can be used to probe the strength of these effects; however, mass data in the region is sparse. In this talk, I will present results from the first Penning trap mass measurement of ⁸⁰Zr using the Low Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory. Our measurement reveals a significant enhancement in the binding energy of ⁸⁰Zr. Through binding-energy indicators, we attribute this enhancement to the deformed double shell closure at N=Z=40 and an increase in the Wigner energy of this exotic system. A statistical Bayesian model mixing analysis employing eleven global nuclear mass models demonstrates difficulties with reproducing the observed mass anomaly using current theory.