The East Lansing Model: Towards uncertainty-quantified optical potentials for rare isotopes

par Dr Kyle Beyer (FRIB/MSU)

lundi 24 nov. 2025, 11:00 → 12:00 Europe/Paris

100/2-A201 - Salle A201 (IJCLab)

Optical potentials are ubiquitous ingredients in nuclear reaction analysis, as they effectively reduce the many-body degrees of freedom to an effective few between reacting bodies. In applications involving nucleon-nucleus optical potentials, this effective interaction is typically obtained by a phenomenological fit to elastic scattering cross sections. Such global phenomenological models have the limitation that the available experimental data to constrain them primarily comes from neutron and proton beams on stable targets. To describe reactions involving species away from beta-stability, with large neutron-proton asymmetry, these models are extrapolated, typically without any uncertainty quantification (UQ). Recently, work has begun to address this lack of UQ using a Bayesian statistical approach. We present the first results of the East Lansing Model (ELM); a global, phenomenological, UQ'ed, nucleon-nucleus optical potential, developed for extrapolating off of the line of beta-stability towards rare isotopes with controlled uncertainties. We discuss the choices made in 1) curating a corpus of experimental evidence from EXFOR including differential cross sections and analyzing powers for (n,n) and (p,p) elastic scattering, and for (p,n) to the isobaric analog state on a variety of targets, 2) developing a functional form for the physical model, 3) developing a model for the likelihood that the physical model describes the evidence, and, finally, 4) performing a Bayesian calibration of the model.  Finally, we demonstrate the performance of ELM compared to the state-of-the-art, highlighting unique features of ELM, especially with regards to its isovector component, which governs the (N-Z)/A dependence.

beyerk_orsay_25.pdf