Charged-particle bound states in periodic boxes

Asymptotic normalization constants (ANC) for nuclei are essential inputs for many low-energy capture reactions that are important in astrophysical environments. We present a new theoretical method that extracts ANCs directly from finite-volume energy spectra for charged-particle systems. Specifically, we consider the finite-volume correction to the binding energy of two-body systems with a repulsive Coulomb interaction. This force is implemented in finite volume by expressing the distance between particles as the shortest separation in a periodic box. The long-range nature of the Coulomb force poses an interesting challenge compared to neutral systems, which we solve with a two-step procedure based on formal perturbation theory. We benchmark our result with explicit numerical calculations and consider the helium-3 system on a lattice with SU(4)-invariant contact interaction.