Super-Soft CP Violation

TL;DR

This paper proposes a new approach to solving the Strong CP Problem using gauge invariance and non-abelian dynamics at the Planck scale, predicting accessible new particles and potential cosmological signatures.

Contribution

It introduces a novel, predictive framework where CP violation arises naturally at small scales without adding new scalars beyond the Standard Model Higgs.

Findings

Vector-like quarks below a few tens of TeV are required for robustness.

The model predicts a dark sector with potential cosmological implications.

CP violation is communicated at super-soft scales, avoiding heavy new state issues.

Abstract

Solutions of the Strong CP Problem based on the spontaneous breaking of CP must feature a non-generic structure and simultaneously explain a coincidence between a priori unrelated CP-even and CP-odd mass scales. We show that these properties can emerge from gauge invariance and a CP-conserving, but otherwise generic, physics at the Planck scale. In our scenarios no fundamental scalar is introduced beyond the Standard Model Higgs doublet, and CP is broken at naturally small scales by a confining non-abelian dynamics. This approach is remarkably predictive: robustness against uncontrollable UV corrections to the QCD topological angle requires one or more families of vector-like quarks below a few $10$'s of TeV, hence potentially accessible at colliders. Because CP violation is communicated to the SM at these super-soft scales, our solution of the Strong CP Problem is not spoiled by the presence of heavy new states motivated by other puzzles in physics beyond the Standard Model. In addition, these models generically predict a dark sector that may lead to interesting cosmological signatures.