Faking ZZZ vertices at the LHC

TL;DR

This paper explores how adding vector-like quarks to the Standard Model can mimic signals of neutral triple gauge couplings at the LHC, potentially affecting searches for new physics in ZZ production.

Contribution

It introduces a simple model with vector-like quarks that can produce ZZ final states similar to NTGC signals, highlighting an alternative background for such searches.

Findings

Vector-like quarks can generate ZZ signals at tree level.

Current and future LHC sensitivities can constrain the model.

Implications for interpreting NTGC search results.

Abstract

Searches for anomalous neutral triple gauge boson couplings (NTGCs) provide important tests for the gauge structure of the standard model. At the LHC, NTGCs are searched for via the process $pp \to ZZ \to 4l$, where the two $Z$-bosons are on-shell. In this paper, we discuss how the same process can occur through tree-level diagrams just adding a vector-like quark (VLQ) to the standard model. Since NTGCs are generated in standard model effective theory (SMEFT) only at 1-loop order, vector like quarks could be an important alternative interpretation to, and background for, NTGC searches. Here, we construct a simple example model, discuss low-energy constraints and estimate current and future sensitivities on the model parameters from $pp \to ZZ \to 4l$ searches.