Alpha Decay Energies of Superheavy Nuclei: Systematic Trends

New superheavy nuclei are often identified through their characteristic $\alpha$-decay energies, which requires accurate calculations of $Q_{\alpha}$ values. While many $Q_{\alpha}$ predictions are available, little is known about their uncertainties, and this makes it difficult to carry out extrapolations to yet-unknown systems. This work aims to analyze several models, compare their predictions to available experimental data, and study their performance for the unobserved $\alpha$-decay chains of $^{296}$120 and $^{298}$120, which are of current experimental interest. Our quantified results will also serve as a benchmark for future, more sophisticated statistical studies. We use nuclear superfluid Density Functional Theory (DFT) with several Skyrme energy density functionals (EDFs). To estimate systematic model uncertainties we employ uniform model averaging. We evaluated the $Q_{\alpha}$ values for even-even nuclei from Fm to $Z=120$. For well deformed nuclei between Fm and Ds, we find excellent consistency between different model predictions, and a good agreement with experiment. For transitional nuclei beyond Ds, inter-model differences grow, resulting in an appreciable systematic error. In particular, our models underestimate $Q_{\alpha}$ for the heaviest nucleus $^{294}$Og. The robustness of DFT predictions for well deformed superheavy nuclei supports the idea of using experimental $Q_{\alpha}$ values, together with theoretical predictions, as reasonable $(Z,A)$ indicators. Unfortunately, this identification method is not expected to work well in the region of deformed-to-spherical shape transition as one approaches $N=184$. The use of $Q_{\alpha}$ values in the identification of new superheavy nuclei will benefit greatly from both progress in developing new spectroscopic-quality EDFs and more sophisticated statistical techniques of uncertainty quantification.