CMS-PAS-HIG-16-026

CMS-PAS-HIG-16-026
Search for non-resonant pair production of Higgs bosons in the $\rm{b} \bar{\rm{b}} \rm{b} \bar{\rm{b}}$ final state with 13 TeV CMS data
CMS Collaboration
August 2016

Abstract: A search for non-resonant Higgs boson pair production in proton-proton collisions at $\sqrt{s}= $ 13 TeV is presented. The Higgs bosons are searched in the $\rm{b} \bar{\rm{b}}$ final state. The data have been collected by the CMS experiment at the LHC during the year 2015, and correspond to an integrated luminosity of 2.32 fb$^{-1}$. No signal is observed and an upper limit of 3880 fb is set on the cross section of non-resonant Higgs pair-production times branching fraction squared of the $\rm{H} \to \rm{b} \bar{\rm{b}}$ decay.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1-a: Two-dimensional plane on which the final shape fit is performed; SM di-Higgs simulation on the left, data collected in 2015 on the right; the z axis shows the number of events; the signal MC is normalized to 1 fb$^{-1}$.
png pdf	Figure 1-b: Two-dimensional plane on which the final shape fit is performed; SM di-Higgs simulation on the left, data collected in 2015 on the right; the z axis shows the number of events; the signal MC is normalized to 1 fb$^{-1}$.
png pdf	Figure 2: Distribution of the BDT output obtained for QCD, ${\mathrm {t}\overline {\mathrm {t}}} $, and SM signal samples for events with at least four b-tags. All components are normalized to one.
png pdf	Figure 3: Comparison of the background distribution as estimated by hemisphere mixing with data from a background-rich control region (i.e. 0.2 $< \rm {BDToutput} <$ 0.4). The dijet mass distributions of the leading and trailing jet are shown.
png pdf	Figure 4: Background-only fit to the data. Post-fit shape uncertainties are shown with a dark shade. For visualization purposes, the expected contribution from 500 $\times $ SM signal is show in red colour.

Tables
png pdf	Table 1: Selection efficiency for the SM like signal; the relative reduction of each successive requirement is shown. The number of expected events for an integrated luminosity of 1 fb$^{-1}$ is also reported.
png pdf	Table 2: Systematic uncertainties considered in the analysis and relative impact on the expected limit for HH production. The relative impact is obtained by fixing the nuisance parameters corresponding to each source and recalculating the expected limit.
png pdf	Table 3: The expected upper limit of $\sigma (\mathrm{ pp \rightarrow H( { { {b}} {\overline { {b}}} } )H( { {{b}} {\overline { {b}}} } ) })$ at 95% confidence level using 2.32 fb$^{-1}$ of data considering the whole set of nuisances.

Summary

A search for non-resonant Higgs boson pair production with both Higgs bosons decaying into $\mathrm{ b \bar{b} }$ pairs is presented. The SM production has been studied using a dataset corresponding to an integrated luminosity of 2.32 fb$^{-1}$ collected at $\sqrt{s} =$ 13 TeV during the year 2015 by the CMS detector. The analysis of events collected by an hadronic multijet trigger includes the selection of events with 4 b-tagged jets, a kinematical selection using the output of a BDT classifier, and the fit of the two-dimensional distribution of reconstructed Higgs boson masses. The background model has been derived by a novel data-driven technique, which provides a precise estimation of the background distribution. As expected, data are well described by background alone; no signal excess is found. The expected upper limit on $\sigma( \mathrm{pp \rightarrow H({ b \bar{b} })H({ b \bar{b} }) })_{\text{SM}}$ is equal to 3490 fb. The observed upper limit is set to 3880 fb, which corresponds to approximately 342 times the expected value for the SM process.

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