# Top quark FCNC couplings at future circular hadron electron colliders

## TL;DR

This paper investigates the potential to detect flavor-changing neutral current interactions involving the top quark at future circular hadron-electron colliders, providing sensitivity estimates for anomalous couplings and decay branching ratios.

## Contribution

It introduces a detailed simulation study of single top production via FCNC at future colliders, estimating upper limits on $tq\gamma$ couplings and improved sensitivity to $t o q\gamma$ decays.

## Key findings

- Upper limit on $\lambda_q$ < 0.01 at 100 fb$^{-1}$
- Enhanced sensitivity to $t o q\gamma$ branching ratio
- Potential to improve current experimental bounds

## Abstract

A study of single top quark production via flavor changing neutral current interactions at $tq\gamma$ vertices is performed at future circular hadron electron collider. The signal cross sections for the processes $e^{-}p\to e^{-}W^{\pm}q+X$ and $e^{-}p\to e^{-}W^{\pm}bq+X$ in the collision of electron beam with energy $E_e=$ 60 GeV and proton beam with energy $E_p=$ 50 TeV are calculated. In the analysis, the invariant mass distributions of three jets reconstructing top quark mass, requiring one b-tagged jet and other two jets reconstructing the $W$ mass are used to count signal and background events after all selection cuts. The upper limits on the anomalous flavor changing neutral current $tq\gamma$ couplings are found to be $\lambda_q < $ 0.01 at future circular hadron electron collider for $L_{int}=100$ fb$^{-1}$ with the fast simulation of detector effects. Signal significance depending on the couplings $\lambda_q$ is analyzed and an enhanced sensitivity is found to the branching ratio BR($t\to q\gamma$) at the future circular hadron electron collider when compared to the current experimental results.