Variational inference of effective range parameters for ³He-⁴He scattering

Journal article, 2025

We use two different methods, Monte Carlo sampling and variational inference (VI), to perform a Bayesian calibration of the effective-range parameters in 3He-4He elastic scattering. The parameters are calibrated to data from a recent set of 3He-4He elastic scattering differential cross section measurements. Analysis of these data for Elab <= 4.3 MeV yields a unimodal posterior for which both methods obtain the same structure. However, the effective-range expansion amplitude does not account for the 7/2- state of 7Be so, even after calibration, the description of data at the upper end of this energy range is poor. The data up to Elab = 2.6 MeV can be well described, but calibration to this lower-energy subset of the data yields a bimodal posterior. After adapting VI to treat such a multi-modal posterior we find good agreement between the VI results and those obtained with parallel-tempered Monte Carlo sampling.