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CMS-PAS-HIG-16-002
Search for resonant pair production of Higgs bosons decaying to two bottom quark-antiquark pairs in proton-proton collisions at 13 TeV
Abstract: A model-independent search for a narrow-width resonance decaying into two Higgs bosons, each having a mass of 125 GeV and decaying into a bˉb pair, is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 2.3 fb1 at s= 13 TeV recorded by the CMS detector at the LHC. No evidence for a signal is observed and upper limits at a 95% confidence level on the production cross section for such a resonance, in the mass range from 260 to 1200 GeV, are set.
Figures & Tables Summary Additional Figures CMS Publications
Figures

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Figure 1:
Illustration of SR and SB in the (mH1, mH2) plane used to motivate and validate the parametric model for the QCD multijet background. The quantities mH1 and mH2 are the two reconstructed Higgs boson masses after b-tagging and kinematic selections for data in medium-mass region.

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Figure 2-a:
The selection efficiency for simulated XH(bˉb)H(bˉb) events (X is a spin-2 RS1 KK-Graviton) at different stages of the event selection for each mass hypothesis, for the low-mass region (a) and the medium-mass region (b).

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Figure 2-b:
The selection efficiency for simulated XH(bˉb)H(bˉb) events (X is a spin-2 RS1 KK-Graviton) at different stages of the event selection for each mass hypothesis, for the low-mass region (a) and the medium-mass region (b).

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Figure 3:
The mX distribution of signal simulated events (spin-2 RS1 KK-Graviton) after the event selection criteria for each of mass hypothesis, with and without the correction by the kinematic constraint to mH.

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Figure 4:
The mX distributions in data in the Signal Region Sideband (SB) of the low-mass region. The distributions are fitted to the GaussExp function and the shaded regions correspond to 1σ variations of the parametrized form.

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Figure 5:
The mX distributions in the control region of data where one of the four jets is required to not be a b-jet. The fits in the SR and SB regions of the medium-mass region are presented.

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Figure 6-a:
The mX distribution in the Signal Region (SR) of data in the LMR (a) and the MMR (b). A fit to the background-only hypothesis, which consists of the QCD multi-jet shape is shown. The shaded region corresponds to a ±1σ variation of this parametrized form. The number of degrees of freedom (n) corresponds to the number of fit parameters (4) subtracted from the number of bins in the histogram.

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Figure 6-b:
The mX distribution in the Signal Region (SR) of data in the LMR (a) and the MMR (b). A fit to the background-only hypothesis, which consists of the QCD multi-jet shape is shown. The shaded region corresponds to a ±1σ variation of this parametrized form. The number of degrees of freedom (n) corresponds to the number of fit parameters (4) subtracted from the number of bins in the histogram.

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Figure 7:
The observed and expected upper limits on the cross section for a spin-2 resonance XH(bˉb)H(bˉb) at a 95% confidence level using data corresponding to an integrated luminosity of 2.3 fb1 at s= 13 TeV using the asymptotic CLS method. Theoretical cross sections for the RS1 KK-Graviton, with k/MPl= 0.1, kL= 35, decaying to four b-jets via Higgs bosons are overlaid.
Tables

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Table 1:
Impact of systematic uncertainties on the signal efficiencies in the low-mass region (LMR) and the medium-mass region (MMR).

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Table 2:
The observed and expected upper limit of σ(ppXH(bˉb)H(bˉb)) at a 95% confidence level using 2.3 fb1 of data for the low and medium-mass regimes (LMR and MMR).
Summary
A model-independent search for a narrow-width resonance is presented. No evidence for a signal is observed in the explored mass range between 260 GeV and 1200 GeV. According to these results the RS1 KK-Graviton with kL= 35 , k/MPl= 0.1 and mass above 350 GeV and below 725 GeV, and in the 775-850 GeV mass range is excluded at a 95% confidence level. A similar search, exploiting 17.9 fb1 collected at 8 TeV, has comparable sensitivity [5] and excluded the same model in the 380-800 GeV mass range.
Additional Figures

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Additional Figure 1:
A maximum likelihood fit to the mX distribution of simulated signal events for the 270 GeV mass hypothesis that pass the low-mass region selection criteria. The distribution is fitted to the sum of two Gaussians. Here n is the number of degrees of freedom in the fit.

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Additional Figure 2:
A maximum likelihood fit to the mX distribution of simulated signal events for the 700 GeV mass hypothesis that pass the medium-mass region selection criteria. The distribution is fitted to a Gaussian core smoothly extended on both sides to exponential tails. Here n is the number of degrees of freedom in the fit.

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Additional Figure 3:
The mX distributions in data in the Signal Region Sideband (SB) of the medium-mass region. The distributions are fitted to the GaussExp function and the shaded regions correspond to 1σ variations of the parametrized form.

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Additional Figure 4:
The mX distributions in the control region of data where one of the four jets is required to not be a b-jet. Presented are fits in the SR and SB regions of the low-mass region. All distributions are fitted to the GaussExp function and the shaded regions correspond to 1σ variations of the parametrized form.

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Additional Figure 5:
The observed and expected upper limits on the cross section for a spin-0 resonance ppXH(bˉb)H(bˉb) at a 95% confidence level using data corresponding to an integrated luminosity of 2.3 fb1 at s= 13 TeV using the asymptotic CLS method. Theoretical cross sections for the RS1 radion, with ΛR= 1 TeV , kL= 35, decaying to four b-jets via Higgs bosons are overlaid.
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