CMS-PAS-HIG-17-009

CMS-PAS-HIG-17-009
Search for resonant pair production of Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at 13 TeV
CMS Collaboration
November 2017

Abstract: A search for a narrow-width resonance decaying into two Higgs bosons, each having a mass of 125 GeV and decaying into a $\mathrm{b\bar{b}}$ pair, is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 35.9 fb $^{-1}$ at $\sqrt{s}=$ 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 times branching fraction for such a resonance decaying to two Higgs bosons and each of them to $\mathrm{b\bar{b}}$ are set in the mass range from 260 to 1200 GeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, JHEP 08 (2018) 152. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The selection efficiency for simulated ${\mathrm {X}\to \mathrm {H}(\mathrm {b} \bar{\mathrm {b}})\mathrm {H}(\mathrm {b}\bar{\mathrm {b}})}$ events (X is a spin-2 Bulk KK-Graviton) at different stages of the event selection for each mass hypothesis, for the low-mass region (solid) and the medium-mass region (dashed). The vertical line at 580 GeV shows corresponds to the transition between twe two selections.
png pdf	Figure 2: The $m_X$ distribution of signal simulated events (spin-2 Bulk KK-Graviton) after the event selection criteria for the 450, 750 and 1000 GeV mass hypotheses, with and without the correction by the kinematic constraint to $m_H$ and the specific b-jet energy corrections.
png pdf	Figure 3: Illustration of SR and SB in the ( $m_{H1}$ , $m_{H2}$ ) plane used to motivate and validate the parametric model for the QCD multijet background. The quantities $m_{H1}$ and $m_{H2}$ are the two reconstructed Higgs boson masses after b tagging and kinematic selections for data in medium-mass region.
png pdf	Figure 4: The $m_X$ predicted (blue) distribution in data for the low-mass signal region in the lower fit range and the actual distribution in the signal region (black).
png pdf	Figure 5: The m $_X$ distribution in the sideband (SB) of the medium-mass region is presented in data.
png pdf	Figure 6: The $m_X$ distributions after the LMR selections for prediction of the Signal Region. These distributions are fitted in the two sub-ranges with both nominal and alternative model ([250,330] GeV (left) [285,625] GeV (right)). A fit to the background-only hypothesis, which consists of the QCD multijet shape is shown. The shaded regions correspond to a $\pm$ 1 and 2 $\sigma$ variation of this parametrized form.
png pdf	Figure 6-a: The $m_X$ distributions after the LMR selections for prediction of the Signal Region. These distributions are fitted in the two sub-ranges with both nominal and alternative model ([250,330] GeV). A fit to the background-only hypothesis, which consists of the QCD multijet shape is shown. The shaded regions correspond to a $\pm$ 1 and 2 $\sigma$ variation of this parametrized form.
png pdf	Figure 6-b: The $m_X$ distributions after the LMR selections for prediction of the Signal Region. These distributions are fitted in the two sub-ranges with both nominal and alternative model ([285,625] GeV). A fit to the background-only hypothesis, which consists of the QCD multijet shape is shown. The shaded regions correspond to a $\pm$ 1 and 2 $\sigma$ variation of this parametrized form.
png pdf	Figure 7: The $m_X$ distribution of the QCD multijet component of the background in the Signal Region in data for the MMR. A fit to the background-only hypothesis, which consists of the QCD multijet shape is shown. The shaded regions correspond to a $\pm$ 1 and 2 $\sigma$ variation of this parametrized form.
png pdf	Figure 8: The observed and expected upper limits on the cross section for a spin-2 resonance ${\mathrm {X}\to \mathrm {H}(\mathrm {b}\bar{\mathrm {b}})\mathrm {H}(\mathrm {b}\bar{\mathrm {b}})}$ at a 95% confidence level using data corresponding to an integrated luminosity of 35.9 fb $^{-1}$ at $\sqrt {s} =$ 13 TeV using the asymptotic CL $_S$ method. Theoretical cross section for the Bulk KK-Graviton, with $k/M_{Pl}=$ 0.5, $kl =$ 35, decaying to four b jets via Higgs bosons is overlaid. The transition between LMR and MMR is based on the expected sensitivity, resulting in the observed discontinuity.
png pdf	Figure 9: The observed and expected upper limits on the cross section for a spin-0 resonance ${\mathrm {X}\to \mathrm {H}(\mathrm {b}\bar{\mathrm {b}})\mathrm {H}(\mathrm {b}\bar{\mathrm {b}})}$ at a 95% confidence level using data corresponding to an integrated luminosity of 35.9 fb $^{-1}$ at $\sqrt {s} =$ 13 TeV using the asymptotic CL $_S$ method. Theoretical cross section for the radion, with ${\lambda}bda =$ 3 TeV, $kl=$ 35, and no radion-Higgs boson mixing, decaying to four b jets via Higgs bosons is overlaid. The transition between LMR and MMR is based on the expected sensitivity, resulting in the observed discontinuity.
png pdf	Figure 10: Observed and expected 95% confidence level upper limits on the production cross section times branching fraction for a spin-2 resonance decaying to HH, using data corresponding to an integrated luminosity of 35.9 fb $^{-1}$ at $\sqrt {s} =$ 13 TeV. The results from different searches investigating various combinations of Higgs boson decay modes are reported.
png pdf	Figure 11: Observed and expected 95% confidence level upper limits on the production cross section times branching fraction for a spin-0 resonance decaying to HH, using data corresponding to an integrated luminosity of 35.9 fb $^{-1}$ at $\sqrt {s} =$ 13 TeV. The results from different searches investigating various combinations of Higgs boson decay modes are reported.

Tables
png pdf	Table 1: Definitions of the regions we use in the "ABCD" method to test the functional form as described in text.
png pdf	Table 2: Impact of systematic uncertainties on the signal efficiencies in the low-mass region (LMR) and the medium-mass region (MMR).

Summary

A search for a narrow-width resonance decaying into two Higgs bosons, each having a mass of 125 GeV and decaying into a

$\mathrm{b\bar{b}}$ pair, is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 35.9 fb

$^{\mathrm{-1}}$ at

$\sqrt{s} =$ 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 spin-0 and spin-2 resonances, in the mass range from 260 to 1200 GeV, are set. Using these results, a radion with decay constant of 3 TeV and a bulk graviton with

$k$ set to 0.5

$M_{Pl}$ are excluded at a 95% confidence level in the mass range from 300 to 1100 GeV and 320 to 720 GeV respectively.

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