CP Violation in Hierarchical Yukawa Models

TL;DR

This paper explores how hierarchical Yukawa models in F-theory GUTs can naturally incorporate CP violation through complex phases, linking higher-dimensional theories to observable CKM phase phenomena.

Contribution

It demonstrates that hierarchical Yukawa matrices in F-theory GUT models can produce observable CP-violating phases, including a specific phase imprint, consistent with experimental data.

Findings

Hierarchical Yukawa models can generate large CP-violating phases.

The model's phases are compatible with a phase of π/3 in Yukawa matrices.

The resulting CKM phase aligns with observed CP violation.

Abstract

Because 4-dimensional CP is a good symmetry of many higher-dimensional theories, this suggests the possible existence of a universal CP-violating phase originating from the process of compactification. Such a phase, if it existed, would not be easy to uncover since the phases in Yukawa matrices are not simply related to the observed CKM phase $\delta$. Hierarchical Yukawa models of the type arising in F-theory GUT models provide an interesting exception. Recently, Heckman and Vafa studied a particular F-theory GUT model with hierarchical Yukawa matrices with complex phases of O(1) and showed, by examining the Jarlskog invariant, that this model leads to $\sin \delta \sim O(1)$. A more detailed examination of the model, although confirming their result, is seen to be also compatible with having a phase $\delta_o= \pi/3$ imprinted on the Hermitian Yukawa matrices, leading to $\sin \delta \simeq \sin \delta_o$.