- Open Access
Resolving the structure of bound states using lattice quantum field theories
Phys. Rev. D 114, 054505 – Published 18 September, 2026
DOI: https://doi.org/10.1103/nhbl-t2hv
Abstract
This work presents the first calculation of a two-to-two particle matrix element of a local current within a lattice-regularized quantum field theory. This exploratory calculation is performed using a leading-order pionless effective field theory of two nucleons in a finite 3D spatial volume, where the Hamiltonian can be diagonalized exactly for moderate volumes. By considering a range of couplings where the theory supports a deuteronlike bound state, we determine the finite-volume spectra and matrix elements of the conserved local vector current. Using the Lüscher formalism, we constrain the infinite-volume, purely hadronic amplitude for this theory. Using previously derived formalism, we then map the finite-volume matrix elements to scattering amplitudes describing a reaction coupling two-particle states via a current insertion, . We then use a recently derived relation between this class of amplitudes and the bound-state elastic form factor to directly constrain the infinite-volume form factor. By varying over a range of values of the coupling of the theory, we explore the effects of this analysis for deep- and shallow-bound states. We reproduce the expected result that, for deep-bound states, the finite-volume formalism is largely unnecessary, while for shallow-bound states, it is absolutely critical to obtain a sensible result. We present a detailed outline of the analysis of this class of matrix elements, including the determination of the charge radius of the bound state. In the shallow-bound-state limit, we find good agreement with the prediction stemming from the anomalous threshold.
Physics Subject Headings (PhySH)
- Bound states
- Effective field theory
- Elastic scattering reactions
- Electroweak interactions in nuclear physics
- Few-body systems
- Nonperturbative effects in field theory
- Nuclear forces
- Nuclear reactions
- Nuclear structure & decays
- Nucleon-nucleon interactions
- Nucleus-neutrino interactions
- Form factors
- Lattice field theory
Article Text
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