# Production of extra quarks decaying to Dark Matter beyond the Narrow Width Approximation at the LHC

## TL;DR

This paper investigates the impact of finite width effects in the production and decay of heavy top partner quarks into dark matter at the LHC, challenging the narrow width approximation used in standard searches.

## Contribution

It analyzes the validity of the narrow width approximation in heavy quark decays to dark matter, identifying conditions where it fails and providing insights for experimental strategies.

## Key findings

- Finite width effects can significantly alter production rates.
- Standard narrow width assumptions may be invalid in certain mass and coupling regimes.
- Guidelines for when to consider finite width effects in searches are provided.

## Abstract

This paper explores the effects of finite width in processes of pair production of an extra heavy quark with charge 2/3 (top partner) and its subsequent decay into a bosonic Dark Matter (DM) candidate -- either scalar or vector -- and SM up-type quarks at the Large Hadron Collider (LHC). This dynamics has been ignored so far in standard experimental searches of heavy quarks decaying to DM and we assess herein the regions of validity of current approaches, based on the assumption that the extra quarks have a narrow width. Further, we discuss the configurations of masses, widths and couplings where the latter breaks down.