Solving a Fine-Tuning Problem of the Standard Model through the Introduction of Vector-Like Quarks

TL;DR

This paper proposes extending the Standard Model with vector-like quarks and a complex singlet, along with a flavor symmetry, to address the fine-tuning problem related to quark mixing parameters.

Contribution

It introduces a novel extension of the Standard Model incorporating vector-like quarks and a complex singlet to naturally explain quark mixing.

Findings

Addresses the fine-tuning problem of quark mixing in the Standard Model.

Demonstrates how vector-like quarks generate light quark mixings.

Provides a theoretical framework for flavor symmetry implementation.

Abstract

We emphasise that even in the extreme chiral limit where only the top and bottom quarks acquire mass, quark mixing is physically meaningful. This implies that the natural value of $|V_{13}|^2 + |V_{23}|^2$ is of order one, which is to be compared to its experimental value of order $10^{-3}$ . We show how this fine-tuning problem of the Standard Model can be solved through an extension of the Standard Model where vector-like quarks and a complex singlet are introduced, together with a flavour symmetry. The mixings of the light quarks are generated through the mixing of the vector-like quarks with the standard quarks.