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Seminar | Physics

Uncertainty Quantification for Phenomenological Optical Potentials

PHY Seminar

Abstract: Optical-model potentials (OMPs), which model the interaction between a projectile and a nuclear target, have been an essential reaction theory ingredient for many decades. Though several esteemed phenomenological OMPs are available (including the Koning-Delaroche [KD] and Chapel Hill 89 [CH89] OMPs), none are equipped with well-calibrated uncertainty estimates. As the field moves to unify structure and reactions, tools for reliable uncertainty quantification (UQ) are becoming increasingly important for combining knowledge from multiple avenues. Without reliable UQ, experimentalists, reaction theorists, and evaluators have little way of knowing where to trust their models and where their models break down.

To address this gap, we revisited the classical KD and CH89 OMP analyses and identified two important statistical limitations that hampered the original analyses’ efforts at UQ. We then developed a generic OMP-UQ framework that leverages Markov-Chain Monte Carlo for parameter inference. Using this framework, we assigned well-calibrated uncertainties to KD and CH89, yielding two new UQ-OMP ensembles, KDUQ and CHUQ. Against both the KD/CH89 training data and a large corpus of test data, our UQ versions show improved reliability and interpretability, and in two case studies, we demonstrate how KDUQ and CHUQ can be dropped in for immediate benefit anywhere KD and CH89 are already used. To expedite the inclusion of OMP uncertainty as a standard practice in the field, we provide digital copies of our potentials and related tools for forward uncertainty propagation [see Phys. Rev. C 107 014602 (2023)].