Constraining top quark flavor violation and dipole moments through three and four top quark productions at the LHC

TL;DR

This paper investigates how three- and four-top quark production at the LHC can be used to constrain top quark flavor-changing neutral currents and dipole moments, providing new limits based on simulated and current data.

Contribution

It introduces a method to set upper limits on top quark FCNC branching ratios and dipole moments using three- and four-top production channels at the LHC.

Findings

Upper limits on FCNC branching fractions are established.

Constraints on top quark dipole moments are derived from four-top production data.

Future LHC measurements could further tighten these bounds.

Abstract

In this paper, we examine the sensitivity of the three-top quark production at the LHC to the top quark flavor-changing neutral currents (FCNC) as well as the sensitivity of the four-top production to the strong and weak dipole moments of the top quark. Upper limits at $95\%$ CL on the branching fractions of $\mathcal{B}(t\rightarrow qX)$, where $X = g, Z, \gamma, H$ and $q=u,c$, are set by performing an analysis on three-top events in the same-sign dilepton channel. We consider the main sources of the background processes and a realistic detector simulation is performed at the center-of-mass energy of 14 TeV. In the second part of this work, based on the recent upper limits which have been set on the four-top quark cross section by the ATLAS and CMS collaborations from 13 TeV data, we constrain the top quark strong and weak dipole moments. The bounds on the top quark dipole moments are presented using the future LHC prospects for four-top quark cross section measurement.