Correlation between nuclear isospin asymmetry and $α$-particle preformation probability for superheavy nuclei from a Bayesian inference

Abstract

In the study of $α$ decay within the superheavy nuclear region ($Z \geq 90$ and $N \geq 140$), the $α$-particle preformation probability $P_α$ serves as a crucial physical quantity linking nuclear structure to decay observables. We introduce a phenomenological model incorporating the decay energy $Q_α$, mass number $A$, orbital angular momentum $l$, isospin asymmetry $I$, and unpaired nucleon effect. For the first time, a Bayesian inference method combined with Markov Chain Monte Carlo (MCMC) sampling has been employed to impose global constraints on the model parameters, enabling the systematic and high-precision calculation of $P_α$. The results reveal a significant suppressing effect of isospin asymmetry on $P_α$, a finding independently corroborated by random forest-based feature importance analysis, which identified $I$ as a dominant factor. Furthermore, calculations using the maximum a posteriori (MAP) parameters not only reproduce the shell effect at $N=152$ but also yield $α$ decay half-life predictions in excellent agreement with experimental ones, thereby validating this model universality. This work provides the first global analysis tool for probing the $α$ preformation mechanism in superheavy nuclei, underscores the potential of the Bayesian framework for inverting complex nuclear physics problems, and establishes a reliable theoretical benchmark for guiding future experimental exploration of superheavy nuclei.

Figures (5)

• Figure 1: Posterior distributions of model's global parameters (diagonal panels) and their correlations (off-diagonal panels) extracted from Eq. (\ref{['Eq5']}) using the original uncertainties of the experimental data.
• Figure 2: Posterior distributions of model's global parameters and their correlations extracted from Eq. (\ref{['Eq12']}) using the original uncertainties of the experimental data.
• Figure 3: Relative dependencies of $\alpha$ particle preformation factor on various features.
• Figure 4: The calculation results of the posterior distribution $P_{\alpha}$ of the parameters of for Cf, Es, and Md nuclei based on the model Eq. (\ref{['Eq12']}) are compared with the experimental data.
• Figure 5: The $\alpha$ decay half-lives of Cf, Es, Fm, and Md near $N=152$, as calculated using the posterior distributions of Eq. (\ref{['Eq5']}) and Eq. (\ref{['Eq12']}) along with their corresponding MAP values.