Probing the $CP$ nature of the top-Higgs Yukawa coupling in $t\bar{t}H$ and $tH$ events with $H \to b\bar{b}$ decays using the ATLAS detector at the LHC
- Aad, Georges et al
- arXiv:2303.05974CERN-EP-2022-208
| Yields calculated following a fit with \kprime\ and $\alpha$\ as free parameters, compared to the observed data in all analysis regions. The different backgrounds and the signal are shown in coloured stack. The background component labelled ``other'' corresponds to the production of $W + $~jets, $Z + $~jets, $t\bar{t}W$, $t\bar{t}Z$, $tZq$, $tWZ$, $t\bar{t}t\bar{t}$ and $WW/WZ/ZZ$ events, as in Ref.~\cite{HIGG-2020-23}. The dashed and dotted lines show the sum of \ttH + \tH\ signals for pure \(CP\)-even and \(CP\)-odd hypotheses normalised to the total data yields including all regions. The hashed area around the prediction illustrates the total post-fit uncertainties. In the middle panel, the best-fit model is compared with the data by showing ratios of its value to the post-fit background prediction. The histogram represents the total post-fit model including the best-fit signals. The hashed band represents the total post-fit uncertainty as a ratio to the background. In the bottom panel, the $S/B$ is shown for pure \(CP\)-even and \(CP\)-odd signals, separately. The histograms are shown as a stack of \ttH\ and \tH. |
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| : The distributions of the fitted variables in all signal regions. The stacked histograms represent the predictions from a fit of signal and background to data with both \kprime\ and $\alpha$ as free parameters. This is compared with data shown with black dots. The solid red histogram shows the best-fit signal with $\alpha=11^\circ$ and $\kprime=0.84$. The dashed and dotted lines show $\ttH+\tH$ signal predictions for pure \(CP\)-even and \(CP\)-odd hypotheses, respectively, normalised to the total data yield per region in order to illustrate the shapes of the signal distribution. The hashed area around the prediction illustrates the total post-fit uncertainties. The lower panel shows the ratio of data to the predicted yields from a fit of signal and background in which \kprime\ and $\alpha$ are free parameters. : Caption not extracted |
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| The observed exclusion contours in the $(\kprime\cos\alpha , \kprime\sin\alpha)$ plane. Regions contained in the dashed, dotted and solid lines are compatible with the best-fit results at 1, 2 and 3~$\sigma$ standard deviations. The cross (diamond) represents the \(CP\)-even (\(CP\)-odd) with \kprime=1 and the best-fit result is represented with a pentagram. |