Search for the Standard Model Higgs boson in the H > WW > lvjj decay channel

This is a condensed description with plots for the analysis CMS-HIG-12-003

Abstract

A search for the Standard Model Higgs boson decaying to two W bosons with the subsequent decay to a final state containing one lepton, one neutrino, and two or three jets is presented. The results are based on a data sample corresponding to an integrated luminosity of 5.0/fb of proton-proton collisions at sqrt(s) = 7 TeV and collected with the CMS detector at the CERN LHC. Selections to discriminate between the signal and background events are based on kinematic and topological quantities including the angular spin correlations of the decay products. No evidence for the Higgs boson is found, and at 95% confidence level the SM Higgs boson production in the mass range 327-415 GeV is excluded.

Limits

MVA-based analysis

Higgs mass observed median expected 68% CL band 95% CL band
170 0.8251 1.3047 [0.9416, 1.8122] [0.7079, 2.4078]
180 1.2383 1.3633 [0.9838, 1.8936] [0.7396, 2.5159]
190 1.5522 1.6797 [1.2122, 2.3331] [0.9113, 3.0998]
200 2.0367 1.7109 [1.2347, 2.3765] [0.9283, 3.1575]
250 1.0685 1.4180 [1.0233, 1.9696] [0.7693, 2.6168]
300 1.1958 1.1914 [0.8598, 1.6549] [0.6464, 2.1987]
305 1.1964 1.2031 [0.8683, 1.6711] [0.6528, 2.2203]
310 1.1392 1.1875 [0.8570, 1.6494] [0.6443, 2.1915]
315 1.0454 1.1953 [0.8626, 1.6603] [0.6485, 2.2059]
320 1.0105 1.1680 [0.8429, 1.6223] [0.6337, 2.1555]
325 1.0278 1.1758 [0.8485, 1.6332] [0.6379, 2.1699]
330 0.9644 1.1758 [0.8485, 1.6332] [0.6379, 2.1699]
335 0.9086 1.1094 [0.8006, 1.5409] [0.6019, 2.0473]
340 0.8584 1.0430 [0.7527, 1.4487] [0.5659, 1.9248]
345 0.8093 0.9844 [0.7104, 1.3673] [0.5341, 1.8166]
350 0.7549 0.9102 [0.6568, 1.2642] [0.4938, 1.6797]
400 0.7457 0.8516 [0.6146, 1.1828] [0.4620, 1.5715]
420 1.0744 0.9648 [0.6963, 1.3402] [0.5235, 1.7806]
440 1.3287 1.0195 [0.7358, 1.4161] [0.5531, 1.8815]
450 1.4277 1.0898 [0.7865, 1.5138] [0.5913, 2.0113]
500 1.9854 1.5195 [1.0966, 2.1106] [0.8244, 2.8043]
550 2.0000 2.2109 [1.5956, 3.0710] [1.1995, 4.0802]
600 2.6966 3.3594 [2.4244, 4.6662] [1.8226, 6.1996]

Fit-based analysis

Higgs mass observed median expected 68% CL band 95% CL band
250 2.94 1.98 [1.45, 2.85] [1.07, 3.95]
275 1.92 1.56 [1.13, 2.22] [0.85, 3.08]
300 1.43 1.40 [1.00, 2.00] [0.53, 2.76]
310 1.00 1.24 [0.90, 1.79] [0.59, 2.48]
320 0.75 1.17 [0.82, 1.68] [0.54, 2.31]
330 0.66 1.11 [0.77, 1.58] [0.50, 2.11]
340 0.61 1.05 [0.75, 1.51] [0.39, 2.01]
350 0.62 1.02 [0.72, 1.44] [0.37, 1.93]
360 0.60 1.02 [0.71, 1.45] [0.38, 1.93]
370 0.64 1.01 [0.71, 1.46] [0.38, 2.01]
380 0.69 1.02 [0.73, 1.48] [0.39, 2.05]
390 0.79 1.03 [0.73, 1.48] [0.41, 2.07]
400 0.98 1.07 [0.77, 1.54] [0.41, 2.13]
410 1.15 1.11 [0.80, 1.61] [0.48, 2.24]
420 1.32 1.15 [0.84, 1.67] [0.50, 2.37]
430 1.51 1.20 [0.85, 1.73] [0.57, 2.46]
440 1.73 1.26 [0.91, 1.84] [0.69, 2.61]
450 1.96 1.34 [0.94, 1.94] [0.72, 2.77]
475 2.54 1.48 [1.08, 2.17] [0.92, 3.10]
500 3.16 1.73 [1.28, 2.56] [1.08, 3.71]
525 3.36 1.92 [1.45, 2.86] [1.19, 4.21]
550 3.62 2.36 [1.71, 3.54] [1.45, 5.29]
575 3.87 2.77 [1.94, 4.17] [1.54, 6.40]
600 4.27 3.55 [2.47, 5.53] [1.37, 8.76]

Figures from CMS-HIG-12-003

figure label description
mu_mjj.png Figure 1 (a) png,pdf The invariant mass of the di-jet system after the physics object selection but before optimization, for the case of muons 2-jets sample.
mu_mlvjj.png Figure 1 (b) png,pdf The invariant mass of the four-body system after the physics object selection but before optimization, for the case of muons 2-jets sample.
lin_data_mu_lepNuW_m_KF.png Figure 2(a) png,pdf Fit-based analysis: the observed four-body mass distribution, with background contribution superimposed, after a simple kinematic selection for muon data. The dashed lines represent the expected Higgs signal peak (the SM cross-section has been multiplied by a factor 20 to make it more visible.)
lin_data_e_lepNuW_m_KF.png Figure 2(b) png,pdf Fit-based analysis: the observed four-body mass distribution, with background contribution superimposed, after a simple kinematic selection for electron data. The dashed lines represent the expected Higgs signal peak (the SM cross-section has been multiplied by a factor 20 to make it more visible.)
mu_phi.png Figure 3(top left) png,pdf Variable Φ used as input for the likelihood discriminant.
mu_phib.png Figure 3(top middle) png,pdf Variable Φ1 used as input for the likelihood discriminant.
mu_ha.png Figure 3(top right) png,pdf Variable Θ1 used as input for the likelihood discriminant.
mu_hb.png Figure 3(middle left) png,pdf Variable Θ2 used as input for the likelihood discriminant.
mu_hs.png Figure 3(middle middle) png,pdf Variable Θ* used as input for the likelihood discriminant.
mu_ptlvjj.png Figure 3(middle right) png,pdf Variable PT(WW) used as input for the likelihood discriminant.
mu_etalvjj.png Figure 3(bottom left) png,pdf Rapidity of the WW system used as input for the likelihood discriminant.
mu_mva2j190.png Figure 3(bottom middle) png,pdf Likelihood discriminant for muon plus 2 jet channel with selection optimized for Higgs mass hypothesis 190 GeV.
mu_mva2j500.png Figure 3(bottom right) png,pdf Likelihood discriminant for muon plus 2 jet channel with selection optimized for Higgs mass hypothesis 500 GeV.
H190_Mjj_Muon_2jets_Stacked.png H350_Mjj_Muon_2jets_Stacked.png H500_Mjj_Muon_2jets_Stacked.png Figure 4(a) png pdf, Figure 4(b) png pdf, Figure 4(c) png pdf The di-jet invariant mass distribution with the fit projections, for the muon 2-jet category, after selections optimized for the Higgs mass hypotheses of 190 GeV (a), 350 GeV (b), and 500 GeV (c). The fit doesn't include data points in the test region between the vertical lines.
H190_Mlvjj_Muon_2jets_WpJShape.png H350_Mlvjj_Muon_2jets_WpJShape.png H500_Mlvjj_Muon_2jets_WpJShape.png Figure 5(a) png pdf, Figure 5(b) png pdf, Figure 5(c) png pdf The distribution of the extrapolated background shape in the signal region for the Higgs mass hypothesis of 190 GeV (a), 350 GeV (b), and 500 GeV (c), for muon 2-jets category. The black markers represent the extrapolated points, while the blue curve is the smooth parametrization using an exponential function. The dashed bands show the envelope of the systematic uncertainty in the shape extrapolation.
H190_Mlvjj_Muon_2jets_Stacked.png H190_Mlvjj_Muon_2jets_Pull.png Figure 6(a) png pdf, Figure 6(d) png pdf The WW invariant mass distribution with the fit projections, for the muon 2-jet category, after selection optimized for the Higgs mass hypotheses of 190 GeV. (a) shows the distribution of the four-body invariant mass distribution in the signal region 65 GeV < mjj < 95 GeV. With the kinematic selection used, we expect about 55 signal events in the distribution. (d) shows pull distribution computed as [(Data - Background)/ Background uncertainty].
H350_Mlvjj_Muon_2jets_Stacked.png H350_Mlvjj_Muon_2jets_Pull.png Figure 6(b) png pdf, Figure 6(e) png pdf The WW invariant mass distribution with the fit projections, for the muon 2-jet category, after selection optimized for the Higgs mass hypotheses of 350 GeV. (b) shows the distribution of the four-body invariant mass distribution in the signal region 65 GeV < mjj < 95 GeV. With the kinematic selection used, we expect about 79 signal events in the distribution. (e) shows pull distribution computed as [(Data - Background)/ Background uncertainty].
H500_Mlvjj_Muon_2jets_Stacked.png H500_Mlvjj_Muon_2jets_Pull.png Figure 6(c) png pdf, Figure 6(f) png pdf The WW invariant mass distribution with the fit projections, for the muon 2-jet category, after selection optimized for the Higgs mass hypotheses of 500 GeV. (c) shows the distribution of the four-body invariant mass distribution in the signal region 65 GeV < mjj < 95 GeV. With the kinematic selection used, we expect about 27 signal events in the distribution. (f) shows pull distribution computed as [(Data - Background)/ Background uncertainty].
limit_first.png Figure 7(a) png pdf Observed (solid) and expected (dashed) 95% CL upper limit on the ratio of the production cross section to the SM expectation for the Higgs boson obtained using the asymptotic CLS technique. The 68% and 95% ranges of expectation for the background-only model are also shown with green and yellow bands, respectively. The solid line at 1 indicates the SM expectation. The fit-based limit is shown.
limit_4chan_fullsyst.png Figure 7(b) png pdf Observed (solid) and expected (dashed) 95% CL upper limit on the ratio of the production cross section to the SM expectation for the Higgs boson obtained using the asymptotic CLS technique. The 68% and 95% ranges of expectation for the background-only model are also shown with green and yellow bands, respectively. The solid line at 1 indicates the SM expectation. The likelihood-based limit is shown.

Tables from CMS-HIG-12-003

Table 1: Determination of the mjj shape and normalization. External constraints are assumed Gaussian.

Process Shape External constraint on normalization
W+jets data/MC Unconstrained
Diboson MC Constrained: (NLO) 61.2pb ± 10%
ttbar MC Constrained: (approx. NNLO) 163pb ± 7%
single top MC Constrained: (approx. NNLO) 84.9pb ± 5%
Drell-Yan+jets MC Constrained: (NNLO, mll50GeV) 3048pb ± 4.3%
Multi-jet data Constrained: MET fit in data ± 50% (100%) for electrons (muons)

Table 2: Sources of signal systematics considered in the analysis, with the corresponding magnitude, for the limit extraction.

Source of uncertainty Fit-based analysis Likelihood-based analysis
Higgs line shape 0-30% 0-30%
Cross-section 15-20% 15-20%
Likelihood selection - 7/13%
Luminosity 2.2% 2.2%
Jet energy scale, resolution, and MET 2-3% <1%
Theory acceptances (PDF) 1-2% 1-2%
Lepton trigger eff. 1% 1%
Lepton selection eff. 1-2% 1-2%
Pile-up <1% <1%
b-tag veto <1% -

Additional plots for public talks

From Analysis Note AN-2011/110

figure label description
mu_jetld_pt.png mu_jetnt_pt.png Figure 2 (left) png pdf, Figure 2 (right) png pdf Comparison of the leading jet (left) and the second jet (right) pT distributions from data and MC for the muon+jets selection.
mu_jetld_eta.png Figure 3 (left) png pdf Comparison of the leading jet η distributions from data and MC for the muon+jets selection.
mu_W_muon_pt.png Figure 4 (left) png pdf Comparison of the muon pT distributions from data and MC for the muon+jets selection.
mu_W_muon_eta.png Figure 4 (right) png pdf Comparison of the muon η distributions from data and MC for the muon+jets selection.
mu_W_mt.png Figure 5 (left) png pdf Comparison of the distributions from data and MC of the transverse mass of the muon / MET system for the muon+jets selection.
mu_event_met_pfmet.png Figure 5 (right) png pdf Comparison of the distributions from data and MC of the MET for the muon+jets selection.
el_mjj.png Figure 11 png pdf Comparison of the dijet mass (mJJ) distributions from data and MC for the electron+jets selection.
mu_charge.png Figure 16 png pdf Comparison of the charge of the muon from data and MC for the muon+jets selection.
el_mlvjj.png Figure 24 (left) png pdf Comparison of the four-body invariant mass from data and MC for the electron+jets selection.
kfcompare-Hww190.png Figure 25 (c) png pdf The four-body mass distributions obtained before and after the kinematic fit are reported for the Higgs mass hypothesis of 190 GeV. The mass range is constrained to that used for subsequent template modeling and limit setting.

From Analysis Note AN-2012/029

signalShape_MH400.png Figure 20 (left) png pdf Higgs boson invariant mass shape, as obtained from the simulation, with all the proper weighting factors taken into account. The spectrum is fitted with a double Crystal-Ball function (i.e. a Gaussian core with power law tails on both sides). This smooth function is used as signal input for the limit extraction. A Higgs mass of 400 GeV is assumed.

-- PietroGovoni - 30-Apr-2012

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