Unitarity Relations in the Presence of Vector-Like Quarks

TL;DR

This paper systematically analyzes how adding vector-like quarks to the Standard Model affects the unitarity relations of the CKM matrix, focusing on moduli differences and CP-violating phases.

Contribution

It provides a detailed study of CKM unitarity relations in models with vector-like quarks, highlighting their impact on matrix moduli and imaginary parts of invariant quartets.

Findings

VLQ presence alters CKM moduli differences.

VLQ affects the size of imaginary parts of CKM quartets.

Up-type VLQ can address the unitarity problem in the first row.

Abstract

We study, in a systematic way, the $V_{\text{CKM}}$ unitarity relations which arise in extensions of the three generations Standard Model (3gSM) involving the addition of vector-like quarks (VLQ). In particular, we emphasize the effect of the presence of VLQ on $V_{\text{CKM}}$ moduli differences, as well on the size of the imaginary parts of rephasing invariant $V_{\text{CKM}}$ quartets. We consider the special case where an up-type VLQ is used to attempt at solving the unitarity problem in the first line of $V_{\text{CKM}}$.