Higgs Search in H → ZZ → 2l2q

This is a condensed description with plots for the analysis CMS-HIG-11-017

Abstract

A search for the standard model Higgs boson decaying to two Z bosons with subsequent decay to a final state with two leptons and two quark-jets, $\mathrm{H \to ZZ \to llqq}$, is presented. Data corresponding to an integrated luminosity of 1.6 $\mathrm{fb^{-1}}$ of LHC proton-proton collisions at the center-of-mass energy of $\sqrt{s}=$ 7 TeV. were collected and analyzed by the CMS experiment. The selection to discriminate between signal and background events is based on kinematic and topological quantities, which include the angular spin correlations of the decay products. The events are classified according to probability of the jets to originate from quarks of light or heavy flavor or from gluons. No evidence for a Higgs boson is found and upper limits on the Higgs boson production cross section are set in the range of masses between 226 $\mathrm{GeV/c^2}$ and 600 $\mathrm{GeV/c^2}$.

Main Results

The exclusion limits of the SM Higgs boson in the channel H->ZZ->2l2q are approaching those of the SM expectation. In the absence of the Higgs boson, these limits are expected to reach the SM expectation with the increased LHC luminosity. At the same time, these results along with comparable results from the CMS collaboration obtained with the other channels provide exclusion of the SM Higgs boson at 95% CL in a wide range within the mass window in this search. A range of Higgs masses hypotheses in the SM4 model with the fourth generation are excluded between 226 and 470 GeV at 95% CL.

Text files with limits etc.

Figures from CMS-HIG-11-017

Figure Label Description
Figure 1 pdf, eps, png Diagram describing the production and decay angles in the process $\mathrm{gg \to HZZ \to llqq}$. These angles are defined in the parent particle rest frames (H or Z).
Figure 2a pdf, eps, png Distribution of the dijet invariant mass mjj. Points with error bars show distributions of data after preselection requirements, solid histograms depict the background expectation from simulated events with the different components illustrated. Open histograms indicate the expected distribution for a Higgs boson with mass 400 $\mathrm{GeV/c^2}$, multiplied by a factor of 100 for illustration.
Figure 2b pdf, eps, png Distribution of the flavor tagging category. Points with error bars show distributions of data after preselection requirements, solid histograms depict the background expectation from simulated events with the different components illustrated. Open histograms indicate the expected distribution for a Higgs boson with mass 400 $\mathrm{GeV/c^2}$, multiplied by a factor of 100 for illustration.
Figure 2c pdf, eps, png Distribution of the angular likelihood discriminant. Points with error bars show distributions of data after preselection requirements, solid histograms depict the background expectation from simulated events with the different components illustrated. Open histograms indicate the expected distribution for a Higgs boson with mass 400 $\mathrm{GeV/c^2}$, multiplied by a factor of 100 for illustration.
Figure 2d pdf, eps, png Distribution of the quark-gluon likelihood discriminant. Points with error bars show distributions of data after preselection requirements, solid histograms depict the background expectation from simulated events with the different components illustrated. Open histograms indicate the expected distribution for a Higgs boson with mass 400 $\mathrm{GeV/c^2}$, multiplied by a factor of 100 for illustration.
Figure 3a pdf, eps, png The mZZ invariant mass distribution after final selection in the 0 b-tag category. Points with error bars show distributions of data, solid histograms depict the background expectation from simulated events with the different components illustrated. Also shown is a hypothetical signal with the mass of 400 $\mathrm{GeV/c^2}$ and cross section 3.0 times that of the SM Higgs, which is smaller than but roughly corresponds to exclusion limit obtained in each b-tag category. Solid curved line shows prediction of background from sideband extrapolation procedure.
Figure 3b pdf, eps, png The mZZ invariant mass distribution after final selection in the 1 b-tag category. Points with error bars show distributions of data, solid histograms depict the background expectation from simulated events with the different components illustrated. Also shown is a hypothetical signal with the mass of 400 $\mathrm{GeV/c^2}$ and cross section 3.0 times that of the SM Higgs, which is smaller than but roughly corresponds to exclusion limit obtained in each b-tag category. Solid curved line shows prediction of background from sideband extrapolation procedure.
Figure 3c pdf, eps, png The mZZ invariant mass distribution after final selection in the 2 b-tag category. Points with error bars show distributions of data, solid histograms depict the background expectation from simulated events with the different components illustrated. Also shown is a hypothetical signal with the mass of 400 $\mathrm{GeV/c^2}$ and cross section 3.0 times that of the SM Higgs, which is smaller than but roughly corresponds to exclusion limit obtained in each b-tag category. Solid curved line shows prediction of background from sideband extrapolation procedure.
Figure 4 pdf, eps, png Comparison of the $e\mu jj$ final state in data (points with error bars) and in the simulation (histogram).
Figure 5 pdf, eps, png Observed (dashed) and expected (solid) 95% CL upper limit on the product of the Higgs boson production cross section and the branching fraction of $\mathrm{H\to ZZ}$ using 1.6 $\mathrm{fb^{-1}}$ of data obtained with the $\mathrm{CL_s}$ technique. The 68% and 95% ranges of expectation are also shown with green and yellow bands. The expected product of the SM Higgs production cross section and the branching fraction is shown as a red solid curve with a band indicating theoretical uncertainties at 68%. The same expectation in the SM4 model are shown with a red dashed curve with a band indicating theoretical uncertainties.
Figure 6 pdf, eps, png Observed (dashed) and expected (solid) 95% CL upper limit on the ratio of the Higgs boson production cross section to the SM expectation using 1.6 $\mathrm{fb^{-1}}$ of data obtained with the $\mathrm{CL_s}$ technique. The 68% and 95% ranges of expectation are also shown with green and yellow bands. The solid line at 1 indicates SM expectation.
Figure 7 pdf, eps, png Observed (dashed) and expected (solid) 95% CL upper limit on the ratio of the Higgs boson production cross section to the expectation with the SM4 model using 1.6 $\mathrm{fb^{-1}}$ of data obtained with the $\mathrm{CL_s}$ technique. The 68% and 95% ranges of expectation are also shown with green and yellow bands. The solid line at 1 indicates SM4 expectation.

Additional plots for public talks

Figure Label Description
Figure 8 pdf, eps, png Distribution of $cos\theta_{1}$ for data (points) and Monte Carlo Simulation (histogram).
Figure 9 pdf, eps, png Distribution of $cos\theta_{2}$ for data (points) and Monte Carlo Simulation (histogram).
Figure 10 pdf, eps, png Distribution of $cos\theta^{\ast}$ for data (points) and Monte Carlo Simulation (histogram).
Figure 11 pdf, eps, png Distribution of $\phi$ for data (points) and Monte Carlo Simulation (histogram).
Figure 12 pdf, eps, png Distribution of $\phi_{1}$ for data (points) and Monte Carlo Simulation (histogram).
Figure 13 pdf, eps, png Distribution of theTrack Counting High Efficiency tagging algorithm for data (points) and Monte Carlo simulation (histogram).

Event Displays

Figure Label Description
Figure 14 pdf, jpg, png Event display of a typical Higgs event candidate, consistent with background, with two electrons and two jets in the final state, mZZ = 580 GeV
Figure 15 pdf, jpg, png Event display of a typical Higgs event candidate, consistent with background, with two muons and two jets in the final state, mZZ = 523 GeV
Edit | Attach | Watch | Print version | History: r5 < r4 < r3 < r2 < r1 | Backlinks | Raw View | WYSIWYG | More topic actions
Topic revision: r5 - 2011-08-18 - AndreiGritsan
 
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    CMSPublic All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2021 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
or Ideas, requests, problems regarding TWiki? use Discourse or Send feedback