Search for resonant pair production of Higgs bosons in the $bbZZ$ channel in proton-proton collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$

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Search for resonant pair production of Higgs bosons in the $b b Z Z$ channel in proton-proton collisions at $\sqrt{s} = 13 TeV$

A. M. Sirunyan et al. (CMS Collaboration)

Phys. Rev. D 102, 032003 – Published 12 August 2020

Abstract

A search for the production of a narrow-width resonance decaying into a pair of Higgs bosons decaying into the $b b Z Z$ channel is presented. The analysis is based on data collected with the CMS detector during 2016, in proton-proton collisions at the LHC, corresponding to an integrated luminosity of $35.9 {fb}^{- 1}$ . The final states considered are the ones where one of the $Z$ bosons decays into a pair of muons or electrons, and the other $Z$ boson decays to either a pair of quarks or a pair of neutrinos. Upper limits at 95% confidence level are placed on the production of narrow-width spin-0 or spin-2 particles decaying to a pair of Higgs bosons, in models with and without an extended Higgs sector. For a resonance mass range between 260 and 1000 GeV, limits on the production cross section times branching fraction of a spin-0 and spin-2 resonance range from 0.1 to 5.0 pb and 0.1 to 3.6 pb, respectively. These results set limits in parameter space in bulk Randall-Sundrum radion, Kaluza-Klein excitation of the graviton, and next-to-minimal two-Higgs doublet models (N2HDMs). For specific choices of parameters the N2HDM can be excluded in a mass range between 360 and 620 GeV for a resonance decaying to two Higgs bosons. This is the first search for Higgs boson resonant pair production in the $b b Z Z$ channel.

Received 11 June 2020
Accepted 15 July 2020

DOI:https://doi.org/10.1103/PhysRevD.102.032003

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Physics Subject Headings (PhySH)

Particle decays

Bottom quark Higgs bosons

Hadron colliders

Particles & Fields

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Vol. 102, Iss. 3 — 1 August 2020

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Figure 1
Comparison of the BDT discriminant for $m_{X} = 500$ and 1000 GeV after the final selection in the muon (upper row) and electron (lower row) final states of the $b b ℓ ℓ jj$ channel. The signals of a RS1 radion with mass of 500 (left panels) and 1000 GeV (right panels) are normalized to a cross section of 1 pb for the $p p \to X \to h h$ process. The shaded area represents the combined statistical and systematic uncertainties in the background estimate.
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Figure 2
Pseudotransverse mass of the reconstructed $h h$ candidates, in the $b b ℓ ℓ ν ν$ channel, for data, simulated spin-2 RS1 graviton signal with a mass of 300 GeV, and simulated backgrounds scaled according to the fit results. The upper and lower rows correspond to the muon and electrons channels. For each row, the left and middle plots are for the $Z / γ^{*} + jets$ and $t \bar{t}$ control regions, and the right is for the signal region. The signals are normalized to 1 pb for the $p p \to X \to h h$ process. The shaded area represents the combined statistical and systematic uncertainties in the background estimate.
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Figure 3
Expected (black dashed line) and observed (black solid line) limits on the cross section of resonant $H H$ production times the branching fraction of $H H \to b b Z Z$ as a function of the resonance mass for the $b b ℓ ℓ jj$ (upper row) and $b b ℓ ℓ ν ν$ (lower row) channels, where $H$ can represent either the SM Higgs boson or an additional Higgs boson from an extended electroweak sector. The spin-0 case is shown on the left and the spin-2 case is shown on the right. The red solid line shows the theoretical prediction for the cross section of a RS1 radion with $λ_{R} = 1 TeV$ and $k L = 35$ (left panels) and a RS1 KK graviton with $\tilde{k} = 0.1$ (right panels). In the spin-0 case only, the blue (green) line shows the decays of $H_{3} \to H_{1} H_{1} / H_{1} H_{2} / H_{2} H_{2} \to b b Z Z$ in the N2HDM formulation, with $\tan β = 0.5 (2.0)$ , the scalar $H_{3}$ vev set to 45 GeV, and the mixing angles $α_{1}$ , $α_{2}$ , $α_{3}$ set to 0.76, 0.48, and 1.00, respectively. The correction factor based on the relative partial width of $H_{3}$ to two gluons is around 3.0 (0.7) for $\tan β = 0.5 (2.0)$ . In the lower row, the vertical black dashed line indicates the resonance mass of 450 GeV, a mass point where the BDT used in the analysis is switched from the one trained for low-mass resonance to the one trained for high-mass resonance.
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Figure 4
Expected (black dashed line) and observed (black solid line) limits on the cross section of resonant $H H$ production times the branching fraction of $H H \to b b Z Z$ as a function of the mass of the resonance for the combination of the $b b ℓ ℓ jj$ and $b b ℓ ℓ ν ν$ channels, where $H$ can represent either the SM Higgs boson or an additional Higgs boson from an extended electroweak sector. The spin-0 case is shown on the left and the spin-2 case is shown on the right. The expected limits for each individual channel are shown with a red dashed line for the $b b ℓ ℓ jj$ channel and blue dashed line for the $b b ℓ ℓ ν ν$ channel. The red solid lines show the theoretical prediction for the cross section of a RS1 radion with $λ_{R} = 1 TeV$ and $k L = 35$ (left panel) and a RS1 KK graviton with $\tilde{k} = 0.1$ (right panel). In the spin-0 case only, the blue (green) line shows the decays of $H_{3} \to H_{1} H_{1} / H_{1} H_{2} / H_{2} H_{2} \to b b Z Z$ in the N2HDM formulation, with $\tan β = 0.5 (2.0)$ , the scalar $H_{3}$ vev set to 45 GeV, and the mixing angles $α_{1}$ , $α_{2}$ , $α_{3}$ set to 0.76, 0.48, and 1.00, respectively. The correction factor based on the relative partial width of $H_{3}$ to two gluons is around 3.0 (0.7) for $\tan β = 0.5 (2.0)$ . The vertical black dashed line indicates the resonance mass of 450 GeV, a mass point where the BDT used in the analysis is switched from the one trained for low-mass resonance to the one trained for high-mass resonance.
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Figure 5
The expected and observed exclusion limits at 95% CL on the RS1 radion with $k L = 35$ (RS1 KK graviton) hypothesis in the $λ_{R}$ ( $\tilde{k}$ ) versus mass plane for the individual $b b ℓ ℓ jj$ (red) and $b b ℓ ℓ ν ν$ (blue) channels and their combination (black). The dark green and light yellow expected limit uncertainty bands represent the 68% and 95% confidence intervals. Solid lines represent the observed limits and dashed lines represent the expected limits. The shaded region is excluded by the current limits. The vertical black dashed line indicates the resonance mass of 450 GeV, a mass point where the BDT used in the $b b ℓ ℓ ν ν$ analysis is switched from the one trained for low-mass resonance to the one trained for high-mass resonance.
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Physical Review D

covering particles, fields, gravitation, and cosmology

Search for resonant pair production of Higgs bosons in the $b b Z Z$ channel in proton-proton collisions at $\sqrt{s} = 13 TeV$

A. M. Sirunyan et al. (CMS Collaboration)

Phys. Rev. D 102, 032003 – Published 12 August 2020

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Physical Review D

covering particles, fields, gravitation, and cosmology

Search for resonant pair production of Higgs bosons in the bbZZ channel in proton-proton collisions at s=13 TeV

A. M. Sirunyan et al. (CMS Collaboration)

Phys. Rev. D 102, 032003 – Published 12 August 2020

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Search for resonant pair production of Higgs bosons in the $b b Z Z$ channel in proton-proton collisions at $\sqrt{s} = 13 TeV$