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Entanglement and accidental symmetries in the nucleon-nucleon system

Alma L. Cavallin*, Oliver Thim, and Christian Forssén

  • *Contact author: alma.cavallin@chalmers.se
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Phys. Rev. C 113, 014005 – Published 30 January, 2026

DOI: https://doi.org/10.1103/mlt1-z7t2

Abstract

We study the connection between accidental symmetries in the nuclear interaction and spin entanglement in two-nucleon scattering. Specifically, we incorporate different levels of Wigner SU(4) and Serber symmetries into leading-order potentials derived from chiral effective field theory. We conduct a quantitative analysis by computing the full S matrix, demonstrating that the neutron-proton spin entanglement can be related to the symmetry properties of the interaction and the presence of certain operators and partial waves. Furthermore, we study the order-by-order evolution of the spin entanglement, up to next-to-next-to-leading order in Weinberg power counting, for both neutron-proton and neutron-neutron scattering. Entanglement suppression is not observed in neutron-neutron scattering, which can be attributed to the Pauli principle and the absence of accidental symmetries in this system. We conclude that entanglement is a useful guide for studying the power counting and symmetries in nuclear interactions derived from effective field theories.

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Phys. Rev. C 113, 014005– Published 30 January, 2026
  • Received 22 October 2025
  • Accepted 8 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.

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