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Nelson-Barr models with vectorlike quark doublets

G. H. S. Alves1,*, C. C. Nishi2,†, and L. Vecchi3,‡

  • 1Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09.210-170, Santo André, São Paulo, Brazil
  • 2Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, 09.210-170, Santo André, São Paulo, Brazil
  • 3INFN, Sezione di Padova, Via Marzolo 8, Padova, 35131, Italy

  • *Contact author: alves.gustavo@ufabc.edu.br
  • †Contact author: celso.nishi@ufabc.edu.br
  • ‡Contact author: luca.vecchi@pd.infn.it
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Phys. Rev. D 114, 015025 – Published 16 July, 2026

DOI: https://doi.org/10.1103/sy92-fyjf

Abstract

We investigate Nelson-Barr (NB) solutions to the strong CP problem in which spontaneous CP violation is transmitted to the Standard Model (SM) through mixing with a vectorlike partner of the SM quark doublet. We show that these constructions constitute compelling and phenomenologically viable alternatives to the more widely studied singlet-based NB models. A key result of our analysis is that an accidental symmetry of the renormalizable theory delays the leading contributions to θ¯ until three loops, naturally suppressing hadronic CP violation. We outline the main phenomenological constraints, including future electric dipole moment experiments, as well as the main differences between these scenarios and generic models with doublet vectorlike quarks.

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Phys. Rev. D 114, 015025– Published 16 July, 2026
  • Received 23 April 2026
  • Accepted 15 June 2026
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