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| CMS-PAS-TOP-17-003 | ||
| Search for the flavor-changing interactions of the top quark with the Higgs boson in $\mathrm{ H \to b\bar{b} }$ channel at $\sqrt{s}= $ 13 TeV | ||
| CMS Collaboration | ||
| September 2017 | ||
| Abstract: A search for flavor-changing neutral currents (FCNC) in associated production of a top quark with a Higgs boson is presented. Two channels are considered: top quark pair production, with FCNC decay of the top quark or antiquark, and single top production ($\mathrm{ pp \to tH }$). This is the first analysis to probe top-Higgs FCNC couplings in the single top production mode. A final state with one isolated lepton and at least three reconstructed jets, among which at least two are identified as b quark jets, is studied. The data sample corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded by the CMS experiment at the LHC in proton-proton collisions at $\sqrt{s}= $ 13 TeV in 2016. No significant deviation is observed from predicted background. Observed (expected) upper limits at 95% confidence level are set on the branching ratios of top quark decays, $B(\mathrm{ t \rightarrow u H }) < $ 0.47% (0.34%) and $B(\mathrm{ t \rightarrow c H }) < $ 0.47% (0.44%), assuming a single non-vanishing FCNC coupling. | ||
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Links:
CDS record (PDF) ;
inSPIRE record ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, JHEP 06 (2018) 102. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Representative Feynman diagrams for FCNC top-Higgs processes: associated production of the top quark with the Higgs boson (left) and FCNC decay of the top quark in $ {\mathrm{t} {}\mathrm{\bar{t}}} $ (right). |
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Figure 1-a:
Representative Feynman diagrams for FCNC top-Higgs processes: associated production of the top quark with the Higgs boson (left) and FCNC decay of the top quark in $ {\mathrm{t} {}\mathrm{\bar{t}}} $ (right). |
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Figure 1-b:
Representative Feynman diagrams for FCNC top-Higgs processes: associated production of the top quark with the Higgs boson (left) and FCNC decay of the top quark in $ {\mathrm{t} {}\mathrm{\bar{t}}} $ (right). |
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Figure 2:
Comparison between data and MC for the most important BDT input variables: lepton charge (top left), CSVv2 discriminant value for one of the reconstructed b jets assigned to Higgs decay (top right), reconstructed mass of the Higgs boson (bottom left) and the maximum BDT score value from the b jet assignment procedure (bottom right). Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
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Figure 2-a:
Comparison between data and MC for the most important BDT input variables: lepton charge (top left), CSVv2 discriminant value for one of the reconstructed b jets assigned to Higgs decay (top right), reconstructed mass of the Higgs boson (bottom left) and the maximum BDT score value from the b jet assignment procedure (bottom right). Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 2-b:
Comparison between data and MC for the most important BDT input variables: lepton charge (top left), CSVv2 discriminant value for one of the reconstructed b jets assigned to Higgs decay (top right), reconstructed mass of the Higgs boson (bottom left) and the maximum BDT score value from the b jet assignment procedure (bottom right). Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 2-c:
Comparison between data and MC for the most important BDT input variables: lepton charge (top left), CSVv2 discriminant value for one of the reconstructed b jets assigned to Higgs decay (top right), reconstructed mass of the Higgs boson (bottom left) and the maximum BDT score value from the b jet assignment procedure (bottom right). Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 2-d:
Comparison between data and MC for the most important BDT input variables: lepton charge (top left), CSVv2 discriminant value for one of the reconstructed b jets assigned to Higgs decay (top right), reconstructed mass of the Higgs boson (bottom left) and the maximum BDT score value from the b jet assignment procedure (bottom right). Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 3:
BDT output score distributions for different jet categories for Hut training after the fit to data. All background processes are constrained to the SM expectation in the fit. To compare the shapes, each of the signal distributions is normalized to the total number of events in the predicted background. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 3-a:
BDT output score distributions for different jet categories for Hut training after the fit to data. All background processes are constrained to the SM expectation in the fit. To compare the shapes, each of the signal distributions is normalized to the total number of events in the predicted background. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 3-b:
BDT output score distributions for different jet categories for Hut training after the fit to data. All background processes are constrained to the SM expectation in the fit. To compare the shapes, each of the signal distributions is normalized to the total number of events in the predicted background. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 3-c:
BDT output score distributions for different jet categories for Hut training after the fit to data. All background processes are constrained to the SM expectation in the fit. To compare the shapes, each of the signal distributions is normalized to the total number of events in the predicted background. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 3-d:
BDT output score distributions for different jet categories for Hut training after the fit to data. All background processes are constrained to the SM expectation in the fit. To compare the shapes, each of the signal distributions is normalized to the total number of events in the predicted background. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 4:
BDT output score distributions for different jet categories for Hct training after the fit to data. All background processes are constrained to the SM expectation in the fit. Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 4-a:
BDT output score distributions for different jet categories for Hct training after the fit to data. All background processes are constrained to the SM expectation in the fit. Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 4-b:
BDT output score distributions for different jet categories for Hct training after the fit to data. All background processes are constrained to the SM expectation in the fit. Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 4-c:
BDT output score distributions for different jet categories for Hct training after the fit to data. All background processes are constrained to the SM expectation in the fit. Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 4-d:
BDT output score distributions for different jet categories for Hct training after the fit to data. All background processes are constrained to the SM expectation in the fit. Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
png pdf |
Figure 4-e:
BDT output score distributions for different jet categories for Hct training after the fit to data. All background processes are constrained to the SM expectation in the fit. Each of the signal distributions is normalized to the total number of events in the predicted background to ease the comparison of the shapes. The shaded area corresponds to a total uncertainty on the predicted background. |
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Figure 5:
Excluded signal cross section at 95% CL per event category for Hut (left) and Hct (right). |
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Figure 5-a:
Excluded signal cross section at 95% CL per event category for Hut (left) and Hct (right). |
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Figure 5-b:
Excluded signal cross section at 95% CL per event category for Hut (left) and Hct (right). |
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Figure 6:
Upper limits on $B(\mathrm{ t \rightarrow u H })$ and $B(\mathrm{ t \rightarrow c H })$ at 95% CL. |
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Figure 7:
The best fit signal strength for Hut (left) and Hct (right). The signal strength is restricted to positive values in the fit. |
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Figure 7-a:
The best fit signal strength for Hut (left) and Hct (right). The signal strength is restricted to positive values in the fit. |
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Figure 7-b:
The best fit signal strength for Hut (left) and Hct (right). The signal strength is restricted to positive values in the fit. |
| Tables | |
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Table 1:
Number of events in each category together with its total relative uncertainty as obtained from the fit to data for Hut. |
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Table 2:
Number of events in each category together with its total relative uncertainty as obtained from the fit to data for Hct. |
| Summary |
| A search for flavor-changing neutral currents in events with the top quark and the Higgs boson corresponding to a data sample of 35.9 fb$^{-1}$ collected in proton-proton collisions at $\sqrt{s}= $ 13 TeV is presented. This is the first search to probe top-Higgs FCNC couplings in both associated production of the top quark with the Higgs boson and in top quark decays. Observed (expected) upper limits at 95% confidence level are set on the branching ratios of top quark decays, $B(\mathrm{ t \rightarrow u H }) < $ 0.47% (0.34%) and $B(\mathrm{ t \rightarrow c H }) < $ 0.47% (0.44%). Inclusion of the associated production of a single top quark with a Higgs boson in this study provides a $\simeq$20% relative improvement in the upper limit on $B(\mathrm{ t \rightarrow uH })$. |
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