Single Higgs boson production in association with a top quark through FCNSI

TL;DR

This study investigates the potential detection of a single Higgs boson produced with a top quark via Flavor-Changing Neutral Scalar Interactions in the context of the Two-Higgs Doublet Model type III at the HL-LHC, using machine learning techniques.

Contribution

It explores the feasibility of observing FCNSI-induced Higgs production with top quarks at the HL-LHC, providing predictions for signal significance under specific model parameters.

Findings

Signal significance of 5σ at certain parameters and luminosities.

Predicted signal significance of approximately 4.4σ under upper limit conditions.

Identification of parameter space regions where detection is promising.

Abstract

We study the production and possible detection of a single Higgs boson in association with a top quark in proton-proton collisions ($pp \to th + X$) at the High-Luminosity Large Hadron Collider. This process absent in the Standard Model is predicted by other models such as the Two-Higgs Doublet Model of type III, which is the theoretical framework adopted in this work. Promising results are found for specific scenarios of the model parameter space, which consist mainly of the parameters $\tan\beta$, $\cos(\alpha-\beta)$ and the parameter $\chi_{tc}$, responsible for the Flavor-Changing Neutral Scalar Interactions (FCNSI). Using the machine learning \textit{Boosted Decision Trees} algorithm and considering a systematic uncertainty of $5\%$, we predict \textit{signal significances} at level of $5\sigma$ for $\tan\beta=1$, $\cos(\alpha-\beta)=0.1$, $\chi_{tc}=5$, and integrated luminosities {$\mathcal{L}_{\rm int}\gtrsim2700~fb^{-1}$}. Likewise, we also predict a \textit{signal significance} $\sigma\approx 4.4$ for $\tan\beta=1$, $\cos(\alpha-\beta)=0.1$, $\chi_{tc}=3$, and integrated luminosities $\mathcal{L}_{\rm int} = 3000~fb^{-1}$, which consider the upper limit given by HL-LHC projection on $\mathcal{BR}(t\to ch)$.