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Pati-Salam realization of the Nelson-Barr mechanism

Clara Murgui

  • Theoretical Physics Department, CERN, 1 Esplanade des Particules, CH-1211 Geneva 23, Switzerland

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Phys. Rev. D 114, 055012 – Published 9 September, 2026

DOI: https://doi.org/10.1103/9xq1-vym3

Abstract

We present a UV completion of the Standard Model in which quarks and leptons are unified under color SU(4). A single fermionic representation, the real antisymmetric, provides the building blocks to address the strong CP problem via the Nelson-Barr mechanism, while simultaneously correcting the charged-lepton and down-quark mass relations predicted by Pati-Salam theories for the two heaviest generations. We show that the characteristic scales of the theory are strongly constrained by its phenomenology. The interplay between the quality of the Nelson-Barr mechanism and the nonobservation of baryon-number-violating processes determines the scale of spontaneous CP violation and the mass of the new vectorlike down quark. The theory predicts a distinctive baryon-number-violating decay mode of the neutron, n→K+ℓ− (with ℓ=e, μ), which lies within the projected sensitivity of upcoming nucleon-decay experiments such as Hyper-Kamiokande, Jiangmen Underground Neutrino Observatory, and the Deep Underground Neutrino Experiment.

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Phys. Rev. D 114, 055012– Published 9 September, 2026
  • Received 14 April 2026
  • Accepted 11 August 2026
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