| Leading-order Feynman diagram for the $T/Y \rightarrow Wb$ process. |
| A representation of the signal, validation, and control regions. Region A1 is the signal region; region A is the validation region and the other four regions B, C, D, and D1 are the control regions. |
| The post-fit distribution for \VLQM in VR A after the fit to data under the background-only hypothesis. All the uncertainties are included in this fit as nuisance parameters. The lower panel depicts the ratio of data to the fitted background yields. |
| The post-fit distribution of \VLQM in the SR A1 after the fit to data under the background-only hypothesis. All the uncertainties are included in this fit as nuisance parameters. The lower panel depicts the ratio of data to the fitted background yields. The hatched area in the lower panel represents the total uncertainty in the background, including the uncertainty in $\mu^{\text{multijets}}$. The overlaid dotted-line histogram in the upper panel shows the signal from a simulated $Y$ VLQ with mass \qty{1.6}{\TeV} and $\kappa=0.5$, normalised to the total post-fit background yield. |
| Expected (dotted) and observed (solid) cross-section limits times branching fraction for a $Y$ VLQ in the $(B,Y)$ doublet as a function of $m_{T/Y}$. Limits are computed for signals with couplings~\subref{fig:k05} $\kappa = 0.5$ and~\subref{fig:k07} $\kappa = 0.7$. The branching fraction $\mathcal{B}(Y \rightarrow Wb)$ is set to 1. The surrounding bands correspond to $\pm 1$ and $\pm 2$ standard deviations around the expected limit. The $T$-singlet quark's theoretical cross-section (corrected to NLO with the inclusion of finite-width effects) times branching fraction ($\mathcal{B} (T \rightarrow Wb) = 0.5)$ as a function of the $T/Y$ mass is also shown (dashed blue line). The mass limit for a $T$ singlet can then be obtained by computing the intersection of those cross-section limits and the $T$-singlet theory cross-section curve. The limits depend on $\kappa$ because the natural width of the $T/Y$ VLQ depends on $\kappa$. |
| Expected (dotted) and observed (solid) cross-section limits times branching fraction for a $Y$ VLQ in the $(B,Y)$ doublet as a function of $m_{T/Y}$. Limits are computed for signals with couplings~\subref{fig:k05} $\kappa = 0.5$ and~\subref{fig:k07} $\kappa = 0.7$. The branching fraction $\mathcal{B}(Y \rightarrow Wb)$ is set to 1. The surrounding bands correspond to $\pm 1$ and $\pm 2$ standard deviations around the expected limit. The $T$-singlet quark's theoretical cross-section (corrected to NLO with the inclusion of finite-width effects) times branching fraction ($\mathcal{B} (T \rightarrow Wb) = 0.5)$ as a function of the $T/Y$ mass is also shown (dashed blue line). The mass limit for a $T$ singlet can then be obtained by computing the intersection of those cross-section limits and the $T$-singlet theory cross-section curve. The limits depend on $\kappa$ because the natural width of the $T/Y$ VLQ depends on $\kappa$. |
| Observed (solid) and expected (dotted) 95\% CL exclusion limits on the coupling constant $\kappa$ as a function of the $Y$ VLQ mass in the $(B,Y)$-doublet scenario. All $\kappa$ values above the black contour lines are excluded at each mass point. The bands correspond to $\pm 1$ and $\pm 2$ standard deviations around the expected limit. Limits are only presented in the regime $\Gamma_{Y}/m_{Y} \leq 50\%$, where the theory calculations are known to be valid. The grey dotted isolines depict the highest $(m, \kappa)$ values allowed for $Y$-doublet signals with various widths up to $\Gamma_{Y}/m_{Y} = 50\%$. |