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  • Letter
  • Open Access

Spin-spin entanglement in diffractive heavy-quark production

Michael Fucilla1 and Yoshitaka Hatta2,3

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Phys. Rev. D 113, L031504 – Published 19 February, 2026

DOI: https://doi.org/10.1103/gbk8-z3dd

Abstract

We calculate the spin density matrix of a heavy-quark-antiquark pair (bb¯, cc¯ or ss¯) diffractively produced in deep inelastic scattering and ultraperipheral collisions. We show that the Pomeron exchange leaves characteristic imprints on the entanglement pattern between the quark and the antiquark. For the longitudinally polarized virtual photon, the pair always exhibits maximal entanglement and maximal violation of the Bell-Clauser-Horne-Shimony-Holt inequality. For the transversely polarized photon, the pair is always entangled and Bell violating, reaching maximal entanglement and maximal violation simultaneously when the transverse momentum approximately equals the quark mass.

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Phys. Rev. D 113, L031504– Published 19 February, 2026
  • Received 12 September 2025
  • Accepted 3 February 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 SCOAP3.

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