# Impact of Rare Decays $t \to \ell' \nu b \ell\ell$ and $t \to q q' b \ell\ell$ on Searches for Top-Associated Physics

## TL;DR

This paper investigates how rare top quark decays can mimic signals in searches for top-associated physics, highlighting potential underestimations of background noise in current LHC analyses.

## Contribution

It identifies and quantifies the impact of specific rare top decays on background estimates in multi-lepton searches at the LHC.

## Key findings

- Rare decays can significantly contribute to background noise.
- Current simulations often overlook these decay channels.
- Underestimation of backgrounds may affect search sensitivities.

## Abstract

Searches for top quark-associated physics such as $t\bar t W$ or $t\bar t H$ in final states with multiple leptons require a careful accounting of expected backgrounds due to the lack of reconstructible resonances. We demonstrate that the rare top quark decays $t \to \ell' \nu b \ell\ell$ and $t \to q q' b \ell\ell$, when a soft lepton is not detected, can contribute a non-negligible background to such searches. Simulations in the LHC experiments typically do not account for such decays and as such backgrounds to such searches may be underestimated.