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

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 >= 8 and N >= 8 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. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

The kernel ridge regression (KRR) approach is extended to include odd-even effects in nuclear mass predictions, resulting in a more accurate mass model. This extended approach achieves a root-mean-square mass deviation of 128 keV, providing the most precise mass model from machine learning approaches yet. Additionally, the extended KRR approach prevents worsening mass predictions for nuclei at large extrapolation distances and ensures smooth extrapolation behavior with respect to odd and even distances.