CMS-PAS-HIG-21-012 | ||
Inclusive search for a boosted Higgs boson and an observation of the Z boson decaying to charm quark pair in proton-proton collisions at √s= 13 TeV | ||
CMS Collaboration | ||
May 2022 | ||
Abstract: A search for the standard model Higgs (H) boson produced with transverse momentum greater than 450 GeV and decaying to charm quark-antiquark pairs (cˉc) is performed using proton-proton collision data collected by the CMS experiment at the LHC at √s= 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb−1. The search is inclusive in H production mode. Highly Lorentz-boosted H decaying to cˉc are reconstructed as single large-radius jets, and are identified using a dedicated charm tagging technique based on a deep neural network. The method is validated with the Z→cˉc decay process, which is observed for the first time in the Z+jets production mode at a hadron collider with a significance of well over 5 standard deviations and a signal strength of 0.91+0.18−0.15 (exp.) ± 0.7 (th.) ± 0.05 (stat.) relative to the standard model prediction. A 95% confidence level observed (expected) upper limit is set on the H→cˉc signal strength of 45 (38) times the standard model prediction. | ||
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CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here. |
Figures | |
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Figure 1:
DDCvL and DDCvB performance for H→cˉc identification versus QCD and H→bˉb processes respectively. No selection apart from the displayed mSD and pT cuts is applied. AUC is the area under curve metric. |
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Figure 2:
The observed and fitted mSD distributions for the passing (left) and failing (right) regions, combining all pT categories, and three data taking years. The fit is performed under the signal-plus-background hypothesis with a single inclusive H(cˉc) signal strength parameter. The QCD yields and shapes and the tˉt yields are estimated from data. The dashed line represents the H→cˉc expectation, amplified by a factor of 200. The step-like features at 166 and 180 GeV occur due to excluded mSD bins, outside of the ρ acceptance region. The lower panel shows the residual difference between the model and data, scaled by the statistical uncertainty in the data, effectively showing an approximate significance. |
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Figure 2-a:
The observed and fitted mSD distributions for the passing region, combining all pT categories, and three data taking years. The fit is performed under the signal-plus-background hypothesis with a single inclusive H(cˉc) signal strength parameter. The QCD yields and shapes and the tˉt yields are estimated from data. The dashed line represents the H→cˉc expectation, amplified by a factor of 200. The step-like features at 166 and 180 GeV occur due to excluded mSD bins, outside of the ρ acceptance region. The lower panel shows the residual difference between the model and data, scaled by the statistical uncertainty in the data, effectively showing an approximate significance. |
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Figure 2-b:
The observed and fitted mSD distributions for the failing region, combining all pT categories, and three data taking years. The fit is performed under the signal-plus-background hypothesis with a single inclusive H(cˉc) signal strength parameter. The QCD yields and shapes and the tˉt yields are estimated from data. The dashed line represents the H→cˉc expectation, amplified by a factor of 200. The step-like features at 166 and 180 GeV occur due to excluded mSD bins, outside of the ρ acceptance region. The lower panel shows the residual difference between the model and data, scaled by the statistical uncertainty in the data, effectively showing an approximate significance. |
Tables | |
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Table 1:
Summary of applied data-to-simulation scale factors for the jet mass scale, jet mass resolution, N1,DDT2 selection, and DDX selections for different data taking periods. Jet mass scale is given as an additive correction in units of GeV. |
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Table 2:
Sources of uncertainty in the measurement of the signal strength μH= 8.6+19.9−19.4, and their observed impact (ΔμH) in the fit to the full data set. The impact of each uncertainty is evaluated by computing the uncertainty excluding that source and subtracting it in quadrature from the total uncertainty. Correlations among the components may prevent the sum in quadrature of each source from matching the total uncertainty. |
Summary |
In conclusion, a search for standard model Z and H bosons produced with transverse momentum greater than 450 GeV and decaying to charm quark-antiquark pairs has been performed with an integrated luminosity of 138 fb−1 at √s= 13 TeV. The Z→cˉc process is observed for the first time in the Z+jets production mode and boosted topology at a hadronic collider. An observed (expected) upper limit on the inclusive Higgs boson cross section times cˉc decay branching ratio of 45 (38) times the standard model expectation is set at the 95% confidence level. |
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Compact Muon Solenoid LHC, CERN |
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