Quantum Monte Carlo calculations of neutron-α scattering via an integral relation

Nuclear physics seeks to describe both bound and unbound states within a unified predictive framework. While coordinate-space quantum Monte Carlo (QMC) methods have successfully computed bound states for systems with A ⩽ 12, their application to unbound states remains limited. In this work, we advance the QMC approach by implementing the integral relations method within the Green’s function Monte Carlo (GFMC) framework, representing a significant methodological advance. This method infers long-range amplitudes in the wave function from integrals over the short-range interaction region. By evaluating these integrals using GFMC wave functions with the Argonne v₁₈ potential, we validate the approach by accurately reproducing neutron–α phase shifts, in agreement with existing benchmarks. This approach provides a systematic pathway for studying more complex nuclear systems, including coupled-channels scattering and the effects of three-nucleon forces. It is a powerful tool for advancing ab initio calculations in nuclear reactions, paving the way for a unified framework that consistently describes bound and scattering states within a single theoretical approach.