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CMS-SUS-17-006 ; CERN-EP-2017-322

Search for physics beyond the standard model in events with high-momentum Higgs bosons and missing transverse momentum in proton-proton collisions at 13 TeV

CMS Collaboration

22 December 2017

Phys. Rev. Lett. 120 (2018) 241801

Abstract: A search for physics beyond the standard model in events with one or more high-momentum Higgs bosons, H, decaying to pairs of b quarks in association with missing transverse momentum is presented. The data, corresponding to an integrated luminosity of 35.9 fb$^{-1}$, were collected with the CMS detector at the LHC in proton-proton collisions at the center-of-mass energy $\sqrt{s} = $ 13 TeV. The analysis utilizes a new b quark tagging technique based on jet substructure to identify jets from $\mathrm{H}\to\mathrm{b}\mathrm{\bar{b}}$. Events are categorized by the multiplicity of H-tagged jets, jet mass, and the missing transverse momentum. No significant deviation from standard model expectations is observed. In the context of supersymmetry (SUSY), limits on the cross sections of pair-produced gluinos are set, assuming that gluinos decay to quark pairs, H (or Z), and the lightest SUSY particle, LSP, through an intermediate next-to-lightest SUSY particle, NLSP. With large mass splitting between the NLSP and LSP, and 100% NLSP branching fraction to H, the lower limit on the gluino mass is found to be 2010 GeV.

Links: e-print arXiv:1712.08501 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ;

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Figures
png pdf	Figure 1: Diagram for production of Higgs bosons via gluino pair production. We also consider channels in which a Z boson is substituted for H in one of the gluino decays.
png pdf	Figure 2: Observed and expected distributions of the leading-$ {p_{\mathrm {T}}}$ jet mass for selected 1H and 2H events with $ {{p_{\mathrm {T}}} ^\text {miss}} > $ 300 GeV. The subleading jet is required to have ${m_{\text {J}}}$ within the signal window denoted by vertical dashed magenta lines. The shape and composition of SM contributions are modeled with simulations while the overall normalization is scaled to the prediction in the signal window. A representative signal is shown stacked on top of the backgrounds. The bottom panel shows the ratio of the observed to SM-expected yields.
png pdf root	Figure 3: Observed and expected cross section upper bounds at 95 CL for the T5HH and T5HZ models. The solid and dashed black lines show the SMS gluino-gluino production cross section with its uncertainty. The solid red (blue) line shows the observed limit for the T5HH (T5HZ) model; for each the like-colored dashed line and shaded band show the expected limit and the range associated with the experimental uncertainties.

Tables
png pdf	Table 1: Correction factors, predicted SM background yields, and observed yields, for the signal regions $A_{N_\mathrm{H}}$. The uncertainties in the predictions include both statistical and systematic contributions.

Summary

In summary, this Letter has presented a search for production of energetic Higgs bosons in conjunction with large missing transverse momentum in proton-proton collisions. Higgs bosons with transverse momentum in the range 300 GeV to about 2 TeV are reconstructed as wide-cone jets with substructure indicative of the decay of the Higgs boson to a pair of b quarks. Background from standard model processes is estimated from data control regions. The observed event yields are found to be statistically compatible with these backgrounds. The results are broadly applicable to models leading to signatures with energetic Higgs bosons and missing momentum. Here they are interpreted in the context of a simplified model of supersymmetry in which gluinos are pair produced and subsequently decay into several quarks, a Higgs or Z boson, and the lightest supersymmetric particle, a neutralino $ \tilde{ \chi }^0_1 $. Gluinos with masses below 2010 (1825) GeV are excluded under the assumption of a large mass splitting between the next-to-lightest and lightest supersymmetric particle and that the branching fraction of $ \tilde{ \chi }^0_2 \to \mathrm{H} \tilde{ \chi }^0_1 $ is 100% (50%). These are the first limits for pair production of gluinos measured in these decay channels.

Additional Figures
png pdf	Additional Figure 1: Signal diagram for the T5ZH model, a topology consisting of boosted Higgs and Z bosons via gluino strong production. We consider a 50% branching fraction to Higgs bosons and a 50% branching fraction to Z bosons.
png pdf	Additional Figure 2: Diagram depicting each of the 6 analysis regions. Those in red signify the high-purity signal regions. Those in blue signify the low-purity sideband regions, which serve to determine the background yields in the high-purity signal regions. The y-axis represents the bb-tagging requirements for the leading and sub-leading jets. The x-axis shows the mass of the leading or sub-leading jet which lies farthest from the center of the Higgs mass window (85,135 GeV).
png pdf	Additional Figure 3: The background composition in each of the six analysis regions, integrated over $ {{p_{\mathrm {T}}} ^\text {miss}} $. The left column shows the three regions with jets in the mass window (85, 135 GeV) (i.e. Regions A1, A2, C). The right column shows the three regions in the mass sideband (50, 85 GeV) and (135, 250 GeV) (i.e. Regions B1, B2, D).
png pdf	Additional Figure 4: Distribution of $ {{p_{\mathrm {T}}} ^\text {miss}} $ in the single-Higgs tagged signal region (A1) comparing the observed yields and background prediction from data.
png pdf	Additional Figure 5: Distribution of $ {{p_{\mathrm {T}}} ^\text {miss}} $ in the double-Higgs tagged signal region (A2) comparing the observed yields and background prediction from data.
png pdf root	Additional Figure 6: Efficiencies for an AK8 jet originating from $\mathrm{H} \rightarrow \mathrm{b} \mathrm{\bar{b}} $ decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for the jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 7: Efficiencies for an AK8 jet originating from $\mathrm{H} \rightarrow \mathrm{W} \mathrm{W} \rightarrow 4\mathrm{q} $ decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 8: Efficiencies for an AK8 jet originating from $\mathrm{H} \rightarrow \mathrm{W} \mathrm{W} \rightarrow \ell \nu 2\mathrm{q} $ decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 9: Efficiencies for an AK8 jet originating from $\mathrm{H} \rightarrow \mathrm{g} \mathrm{g} $ decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 10: Efficiencies for an AK8 jet originating from $\mathrm{H} \rightarrow \mathrm{c} \mathrm{\bar{c}} $ decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 11: Efficiencies for an AK8 jet originating from $\mathrm{Z} \rightarrow \mathrm{b} \mathrm{\bar{b}} $ decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 12: Efficiencies for an AK8 jet originating from $\mathrm{Z} \rightarrow \mathrm{u} \mathrm{d} \mathrm{s} \mathrm{c} $ pair decay, relative to baseline selection. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).
png pdf root	Additional Figure 13: Efficiencies for an AK8 jet originating from W decay (all modes), relative to events with no leptons or isolated tracks. The 'signal mass' curve represents the probability that the jet will fall within the mass region (85, 135 GeV). The 'sideband mass' curve represents the probability that the jet will fall within the mass region (50, 85 GeV) or (135, 250 GeV). The 'H-tag' curve represents the probability for jet to have a double-b discriminator value greater than 0.3, for jets within the mass region (50, 250 GeV).

Additional Tables
png pdf	Additional Table 1: Results table, including the data yields in the 6 analysis ABCD regions. The predicted background for each signal region can be calculated as B*(C/D)*kappa. This prediction assumes no contribution from signal events in the control regions, B, C, and D. If signal is expected from a given model in the B, C, D regions, an adjusted SM background prediction for the signal region can be computed by subtracting the expected signal contribution to regions B, C, and D from the observed yields and recomputing B*(D/C)*kappa with these signal-contamination corrected yields in B, C, and D.
png pdf	Additional Table 2: Cut flow table showing the total yields at 35.9 fb$^{-1}$ for both the T5HH and T5ZH models with gluino masses of 1300 and 2200 GeV.
png pdf	Additional Table 3: Signal event efficiencies for the T5HH model with a 2200 GeV gluino mass. Choosing a gluino mass of 1800 GeV decreases the efficiencies by a relative 5%.

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