Probing the anomalous FCNC interactions in a top-Higgs boson final state and the charge ratio approach

Abstract

We study the anomalous production of a single top quark in association with a Higgs boson at the LHC originating from flavor changing neutral current (FCNC) interactions in $tqg$ and $tqH$ vertices. We derive the discovery potentials and $68\%$ C.L. upper limits considering leptonic decay of the top quark and the Higgs boson decay into a $b\bar{b}$ pair with 10 fb$^{-1}$ integrated luminosity of data in proton-proton collisions at the center-of-mass energy of 14 TeV. We propose a charge ratio for the lepton in top quark decay in terms of lepton $p_{T}$ and $\eta$ as a strong tool to observe the signal. In particular, we show that the charge ratio increases significantly at large $p_{T}$ of the charged lepton. While the main background from $t\bar{t}$ is nearly charge symmetric and $W+jets$ background has much smaller charge ratio with respect to the signal. We show that this feature can also be used in the probe of anomalous single top production with a $Z-$boson or a photon which are under the attention of the experimental collaborations.