Photon initiated single top quark production via flavor-changing neutral currents at the LHC

TL;DR

This paper proposes a new method to search for flavor-changing neutral currents involving the top quark and photon at the LHC, setting new experimental limits and exploring future sensitivities.

Contribution

It introduces a novel search channel for top quark FCNC via photon at the LHC and provides the first experimental limits on certain FCNC top decay branching fractions.

Findings

Set the first experimental limits on ${ m B}(t o u\gamma)$ and ${ m B}(t o c\gamma)$.

Demonstrated the potential sensitivity of the channel at 13 TeV.

Used ATLAS 8 TeV data to constrain FCNC couplings.

Abstract

Single top quark production is a powerful process to search for new physics signs. In this work we propose and investigate a search for top quark flavor changing neutral currents (FCNC) via a photon using direct single top quark production events in proton-proton collisions at the LHC at CERN. We show that the direct single top quark final state can provide constraints on the strengths of tq$\gamma$ (top-quark-$\gamma$) and tqg (top-quark-gluon) FCNC couplings simultaneously. Results of a search for direct single top quark production at the LHC at a center-of-mass energy of 8 TeV performed by the ATLAS collaboration are used to set first experimental limits on the anomalous FCNC top decay branching fractions ${\cal B}$(t$\rightarrow$ u$\gamma$) $<$ 0.05% and ${\cal B}$(t$\rightarrow$ c$\gamma$) $<$ 0.14% via direct single top quark production. Finally, the sensitivity of the proposed channel for probing the tq$\gamma$ couplings at 13 TeV is presented.