A projection-based emulator for nuclear two-body scattering in momentum space*

Projection-based emulators have been game changers in facilitating full Bayesian uncertainty quantification of microscopic interactions derived from chiral effective field theory (EFT). However, their full potential has not been thoroughly explored. Here, we introduce a novel emulator for the Lippmann-Schwinger equation for nuclear two-body scattering with channel coupling using Galerkin projections. The efficacy of the new emulators is demonstrated for half-shell T-matrices and scattering phase shifts based on a simple NN interaction and realistic chiral interaction in momentum space. This set the stage for quantifying emulator uncertainties, which is only in its infancy in nuclear physics.