Nelson-Barr Models with Vector-Like Quark Doublets

TL;DR

This paper explores Nelson-Barr models with vector-like quark doublets, showing they naturally suppress CP violation contributions and are viable alternatives to singlet-based models, with distinct phenomenological features.

Contribution

It introduces a new class of Nelson-Barr models using vector-like quark doublets, demonstrating their natural suppression of CP violation and phenomenological viability.

Findings

Leading contributions to  are delayed until three loops, reducing hadronic CP violation.

These models are compelling and phenomenologically viable alternatives to singlet-based Nelson-Barr models.

Distinct phenomenological constraints and differences from generic doublet vector-like quark models are outlined.

Abstract

We investigate Nelson--Barr solutions to the strong CP problem in which spontaneous CP violation is transmitted to the Standard Model through mixing with a vector-like 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 \bar{\theta} until three loops, naturally suppressing hadronic CP violation. We outline the main phenomenological constraints, including future EDM experiments, as well as the main differences between these scenarios and generic models with doublet vector-like quarks.