Nuclear masses in extended kernel ridge regression with odd-even effects

TL;DR

This paper extends kernel ridge regression to include odd-even effects in nuclear mass predictions, achieving unprecedented accuracy and reliable extrapolation behavior without adding new parameters.

Contribution

The paper introduces an extended KRR method that incorporates odd-even effects without extra parameters, significantly improving nuclear mass prediction accuracy.

Findings

Root-mean-square deviation reduced to 128 keV for 2353 nuclei.

Achieves the most precise machine learning-based nuclear mass model.

Provides smooth and reliable extrapolation for odd and even nuclei.

Abstract

The kernel ridge regression (KRR) approach is extended to include the odd-even effects in nuclear mass predictions by remodulating the kernel function without introducing new weight parameters and inputs in the training network. By taking the WS4 mass model as an example, the mass for each nucleus in the nuclear chart is predicted with the extended KRR network, which is trained with the mass model residuals, i.e., deviations between experimental and calculated masses, of other nuclei with known masses. The resultant root-mean-square mass deviation from the available experimental data for the 2353 nuclei with $Z\ge8$ and $N\ge8$ can be reduced to 128 keV, which provides the most precise mass model from machine learning approaches so far. Moreover, the extended KRR approach can avoid the risk of worsening the mass predictions for nuclei at large extrapolation distances, and meanwhile, it provides a smooth extrapolation behavior with respect to the odd and even extrapolation distances.