Vector-Like Quarks at the LHC: A Unified Perspective from ATLAS and CMS Exclusion Limits

TL;DR

This paper reviews the latest exclusion limits on Vector-Like Quarks from ATLAS and CMS at the LHC, providing a unified overview of bounds across different models and production modes, using a new analysis tool.

Contribution

It offers a comprehensive, updated comparison of VLQ exclusion limits from ATLAS and CMS, employing a new Python tool for systematic analysis across various VLQ representations.

Findings

Excludes VLQ masses up to 1.52 TeV for certain models.

Constrains mixing parameter κ below 0.26 for top-like VLQs.

Provides a unified perspective on VLQ search results.

Abstract

In this work, we present a comprehensive review of the most up-to-date exclusion limits on Vector-Like Quarks (VLQs) derived from ATLAS and CMS data at the Large Hadron Collider (LHC). Our analysis encompasses both pair and single production modes, systematically comparing results from the two collaborations to identify and employ the most stringent bounds at each mass point. We evaluate the excluded parameter space for VLQs under singlet, doublet, and triplet representations. For top-like VLQs ($T$), the exclusion limits rule out masses up to 1.49 TeV in singlet scenarios, while single production constrains the mixing parameter $\kappa$ to values below 0.26 at $m_T \sim 1.5$ TeV and up to 0.42 for $m_T \sim 2$ TeV. For bottom-like VLQs ($B$), the strongest exclusion limits from pair production exclude masses up to 1.52 TeV in doublet configurations, with single production constraining $\kappa$ values between 0.2 and 0.7 depending on the mass. For exotic VLQs, such as $X$ and $Y$, pair production excludes masses up to 1.46 TeV and 1.7 TeV, respectively. The constraints on $\kappa$ from these analyses become increasingly restrictive at higher masses, reflecting the enhanced sensitivity of single production channels in this regime. For $X$, $\kappa$ is constrained below 0.16 for masses between 0.8 and 1.6 TeV and further tightens to $\kappa < 0.2$ as the mass approaches 1.8 TeV. Similarly, for $Y$, $\kappa$ values are constrained below 0.26 around $m_Y \sim 1.7$ TeV, with exclusions gradually relaxing at higher masses. These exclusion regions, derived from the most stringent LHC search results, offer a unified and up-to-date perspective on VLQ phenomenology. The results were computed using \texttt{VLQBounds}, a new Python-based tool specifically developed for this purpose.