Abstract

The charge-parity ($CP$) structure of the Yukawa interaction between the Higgs (H) boson and the top quark is measured in a data sample enriched in the $\mathrm{t\bar{t}}$ and tH associated production, using 138 fb$^{-1}$ of data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV by the CMS experiment at the CERN LHC. The study targets events where the H boson decays via H $\to$ WW or H $\to$$\tau\tau$ and the top quarks decay via t $\to$ Wb: the W bosons decay either leptonically or hadronically, and final states characterized by the presence of at least two leptons are studied. Machine learning techniques are applied to these final states to enhance the separation of $CP$-even from $CP$-odd scenarios. Two-dimensional confidence regions are set on $\kappa_\mathrm{t}$ and $\tilde{\kappa}_\mathrm{t}$, which are respectively defined as the $CP$-even and $CP$-odd top-Higgs Yukawa coupling modifiers. No significant fractional $CP$-odd contributions, parameterized by the quantity $\lvert{f_{CP}^{\mathrm{Htt}}}\rvert$ are observed; the parameter is determined to be $\lvert{f_{CP}^{\mathrm{Htt}}}\rvert$ = 0.59 with an interval of (0.24, 0.81) at 68% confidence level. The results are combined with previous results covering the H $\to$ ZZ and H $\to$ $\gamma\gamma$ decay modes, yielding two- and one-dimensional confidence regions on $\kappa_\mathrm{t}$ and $\tilde{\kappa}_\mathrm{t}$, while $\lvert{f_{CP}^{\mathrm{Htt}}}\rvert$ is determined to be $\lvert{f_{CP}^{\mathrm{Htt}}}\rvert$ = 0.28 with an interval of $\lvert{f_{CP}^{\mathrm{Htt}}}\rvert$ $\lt$ 0.55 at 68% confidence level, in agreement with the standard model $CP$-even prediction of $\lvert{f_{CP}^{\mathrm{Htt}}}\rvert$ = 0.

Figure 3a

Data from Figure 3 (left).

10.17182/hepdata.131043.v2/t1

M_ttH which is one of the input variables to the XGBoost used for CP discrimination in 2lss + 0tau channel,...
Figure 3b

Data from Figure 3 (center).

10.17182/hepdata.131043.v2/t2

\Delta \eta_{B-B}, which is one of the input variables to the XGBoost used for CP discrimination in 2lss + 0tau...
Figure 3c

Data from Figure 3 (right).

10.17182/hepdata.131043.v2/t3

\Delta R_{jet-jet}, which is one of the input variables to the XGBoost used for CP discrimination in 2lss + 0tau...
Figure 4a

Data from Figure 4 (left).

10.17182/hepdata.131043.v2/t4

M_ttH which is one of the input variables to the XGBoost used for CP discrimination in 3l + 0tau channel,...
Figure 4b

Data from Figure 4 (center).

10.17182/hepdata.131043.v2/t5

\Delta \eta_{B-B}, which is one of the input variables to the XGBoost used for CP discrimination in 3l + 0tau...
Figure 4c

Data from Figure 4 (right).

10.17182/hepdata.131043.v2/t6

\Delta R_{l1-l2}, which is one of the input variables to the XGBoost used for CP discrimination in 3l + 0tau...
Figure 6a

Data from Figure 6 (upper)

10.17182/hepdata.131043.v2/t7

Postfit discriminating distributions used as input to the fit. Events in the tH{} node are caregorized in bins of CP...
Figure 6b

Data from Figure 6 (middle)

10.17182/hepdata.131043.v2/t8

Postfit discriminating distributions used as input to the fit. Events in the tH{} node are caregorized in bins of CP...
Figure 6c

Data from Figure 6 (lower)

10.17182/hepdata.131043.v2/t9

Postfit discriminating distributions used as input to the fit. Events in the tH{} node are caregorized in bins of CP...
Figure 7a

Data from Figure 7 (left).

10.17182/hepdata.131043.v2/t10

Expected likelihood scan as a function of kappa_t and #tilde{kappa_t}
Figure 7b

Data from Figure 7 (right).

10.17182/hepdata.131043.v2/t11

Observed likelihood scan as a function of kappa_t and #tilde{kappa_t}
Figure 8

Data from Figure 8.

10.17182/hepdata.131043.v2/t12

Likelihood scan as a function of |f_{CP}^{Htt}| for multilepton final states
Figure 9a

Data from Figure 9 (left).

10.17182/hepdata.131043.v2/t13

Expected likelihood scan as a function of |f_{CP}^{Htt}| for multilepton, #gamma#gamma+ZZ final states and the combniation.
Figure 9b

Data from Figure 9 (right).

10.17182/hepdata.131043.v2/t14

Observed likelihood scan as a function of |f_{CP}^{Htt}| for multilepton final states and the combniation.
Figure 10

Data from Figure 10.

10.17182/hepdata.131043.v2/t15

Likelihood scan as a function of kappa_t and #tilde{kappa_t} for multilepton final states and the combination with #gamma#gamma and ZZ...

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