CMS-HIG-17-030

CMS-HIG-17-030 ; CERN-EP-2018-292
Combination of searches for Higgs boson pair production in proton-proton collisions at $\sqrt{s} = $ 13 TeV
CMS Collaboration
23 November 2018
Phys. Rev. Lett. 122 (2019) 121803
Abstract: This Letter describes a search for Higgs boson pair production using the combined results from four final states: $ {\mathrm{b}\mathrm{b}\gamma\gamma} $, $ {\mathrm{b}\mathrm{b}\tau\tau} $, $ {\mathrm{b}\mathrm{b}\mathrm{b}\mathrm{b}} $, and $ {\mathrm{b}\mathrm{b} \text{VV}} $, where V represents a W or Z boson. The search is performed using data collected in 2016 by the CMS experiment from LHC proton-proton collisions at $\sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Limits are set on the Higgs boson pair production cross section. A 95% confidence level observed (expected) upper limit on the nonresonant production cross section is set at 22.2 (12.8) times the standard model value. A search for narrow resonances decaying to Higgs boson pairs is also performed in the mass range 250-3000 GeV. No evidence for a signal is observed, and upper limits are set on the resonance production cross section.
Links: e-print arXiv:1811.09689 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: The 95% CL upper limits on the signal strength $\mu =\sigma _{\mathrm{HH}} /\sigma _{\mathrm{HH}} ^\text {SM}$. The inner (green) band and the outer (yellow) band indicate the regions containing 68 and 95%, respectively, of the limits on $\mu $ expected under the background-only hypothesis.
png pdf	Figure 2: Expected and observed 95% CL upper limits on the HH production cross section as a function of the $k_\lambda $ parameter. The inner (green) band and the outer (yellow) band indicate the regions containing 68 and 95%, respectively, of the limits on the HH cross section expected under the background-only hypothesis. The red band shows the expected theoretical [26] cross section expectations and its uncertainty. All other couplings and EFT parameters are set to their SM values.
png pdf	Figure 3: Expected (dashed) and observed (solid line) 95% CL exclusion limits on the production of a narrow, spin zero resonance (X) decaying into a pair of Higgs bosons. The inner (green) band and the outer (yellow) band indicate the regions containing 68 and 95%, respectively, of the limits on the HH cross section expected under the background-only hypothesis.
png pdf	Figure 4: The 95% CL exclusion limits on the nonresonant Higgs boson pair production cross sections for different EFT benchmark topologies (bins 1 to 12) as defined in Ref. [26]. Each benchmark represents a possible modification in the HH signal yield and kinematic distributions due to BSM effects. The last two bins show the 95% CL exclusion limits for the SM and for the $k_\lambda =$ 0 scenarios. Limits are shown for each of the four final states separately and for the combination.
png pdf	Figure 5: The 95% CL exclusion limits on the nonresonant Higgs boson pair production cross sections for different EFT benchmark topologies. Each bin of the histogram shows the limit for a different benchmark (bins 1 to 12) as defined in Ref. [26], for SM production and for $k_\lambda =$ 0 production (last 2 bins). Each benchmark represents a possible modification in the HH signal yield and kinematic distributions due to BSM effects.
png pdf	Figure 6: The 95% CL exclusion limits on the SM nonresonant Higgs boson pair production cross section for different channels. The inner (green) band and the outer (yellow) band indicate the regions containing 68 and 95%, respectively, of the distribution of limits expected under the background-only hypothesis. The uppermost bin reports the combined limit obtained at $\sqrt {s}=$ 8 TeV.
png pdf	Figure 7: Expected (dashed) and observed (solid line) 95% CL exclusion limits on the production of a narrow, spin-2 resonance decaying into a pair of Higgs bosons. The inner (green) band and the outer (yellow) band indicate the regions containing 68 and 95%, respectively, of the distribution of limits expected under the background-only hypothesis.

Summary

In summary, a combination of searches for nonresonant and resonant Higgs boson pair production has been presented. The combination includes the $ {\mathrm{b}\mathrm{b}\gamma\gamma} $, $ {\mathrm{b}\mathrm{b}\tau\tau} $, $ {\mathrm{b}\mathrm{b}\mathrm{b}\mathrm{b}} $, and $ {\mathrm{b}\mathrm{b} \text{VV}} $ channels, where V represents a W or Z boson, using a data sample collected in proton-proton collisions at $\sqrt{s} = $ 13 TeV, which corresponds to an integrated luminosity of 35.9 fb$^{-1}$. Upper limits at 95% confidence level (CL) on the Higgs boson pair production cross section are obtained. For the nonresonant production mechanism, the observed (expected) 95% CL corresponds to 22.2 (12.8) times the theoretical prediction for the standard model cross section. An effective field theory framework is used to parametrize the cross section as a function of anomalous couplings of the Higgs boson. When varying only the ratio $k_\lambda$ between the Higgs trilinear coupling $ \lambda_{\mathrm{HHH}} $ and its standard model (SM) expectation, values of $k_\lambda$ in the region $-11.8

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