Spontaneous CP violation in Supersymmetric QCD

TL;DR

This paper proposes a supersymmetric QCD model where spontaneous CP violation occurs through complex vacuum expectation values, generating the CKM phase while protecting the strong CP phase, offering a solution to the strong CP problem.

Contribution

It introduces a novel composite model with spontaneous CP violation in supersymmetric QCD, explaining the CKM phase and protecting the strong CP phase without fine-tuning.

Findings

The model generates the CKM phase via wavefunction renormalization.

The strong CP phase is protected by nonrenormalization and hermiticity.

A viable parameter space exists for solving the strong CP problem.

Abstract

We investigate a composite model of spontaneous CP violation based on a new supersymmetric QCD as a solution to the strong CP problem. The scalar components of the meson chiral superfields obtain complex vacuum expectation values to break CP symmetry spontaneously. Then, wavefunction renormalization for the quark kinetic terms provides the Cabibbo-Kobayashi-Maskawa (CKM) phase, while the strong CP phase $\bar{\theta}$ is protected by nonrenormalization of the superpotential and hermiticity of the wavefunction renormalization factor. In our model, the right-handed down-type quark multiplets are given by composite states, enhancing their couplings to CP breaking fields, which is essential to realize the observed CKM phase. The non-perturbative dynamics generates the scale of spontaneous CP violation hierarchically lower than the Planck scale. We discuss potential corrections to $\bar{\theta}$ and find a viable parameter space of the model to solve the strong CP problem without fine-tuning.