Observation of a resonance with a mass near 125 GeV in the search for the Higgs boson in pp collisions at √s = 7 TeV and 8 TeV.
This is a condensed description with plots for the analysis CMSHIG12020
Abstract
Combined results are reported from searches for the standard model Higgs boson in protonproton collisions at √s = 7 TeV and 8 TeV in five final state modes: γγ, bb, ττ, WW, and ZZ. The analysed data correspond to integrated luminosities up to 5.1 fb^{–1} at 7 TeV and 5.3 fb^{–1} at 8 TeV .
The data exclude the existence of a SM
Higgs boson in the ranges 110–122.5, 127–600 GeV at 95% confidence level. An excess
of events above the expected SM background is observed with a local significance of
4.9σ for a Higgs boson mass hypothesis of around 125 GeV. We interpret this to be
due to the production of a previously unobserved particle with a mass of around
125 GeV. The evidence is strongest in the two final states with the best mass resolution:
firstly the twophoton final state and secondly the final state with two pairs of
charged leptons (electrons or muons). The excess in these final states alone, above the
expected SM background, gives a local significance of 5.0σ. An unconstrained fit to
these excesses yields a mass of 125.3 ± 0.4 (stat) ± 0.5 (syst) GeV. Within the statistical
uncertainties, the results obtained in the different search channels are consistent
with the expectations for a SM Higgs boson. More data are needed to test whether
this new state has all the properties of the SM Higgs boson or whether some do not
match, implying new physics beyond the standard model.
Sensitivities
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The median expected 95% CL upper limits on the cross section ratio σ/σ_{SM} in the absence of a Higgs boson as a function of the SM Higgs boson mass in the range 110–600 GeV (left) and 110–145 GeV (right), for the five Higgs boson decay channels. Here σ_{SM} denotes the cross section predicted for the SM Higgs boson. A channel showing values below unity (dotted red line) would be expected to be able to exclude a Higgs boson of that mass at 95% CL. The jagged structure in the limits for some channels results from the different event selection criteria employed in those channels for different Higgs boson mass subranges. 

The median expected pvalue for observing an excess at mass m_{H} in assumption that the SM Higgs boson with this mass exists, as a function of the SM Higgs boson mass in the range 110–600 GeV (left) and 110–145 GeV (right). Expectations for subcombinations in five Higgs boson decay channels and the overall combination are shown. 
Additional plots
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The median expected pvalue for observing an excess at mass m_{H} in assumption that the SM Higgs boson with this mass exists, as a function of the SM Higgs boson mass in the range 110–600 GeV (left) and 110–145 GeV (right). Expectations for the two subcombinations of low mass resolution and high mass resolution channels are shown. 

The median expected pvalue for observing an excess at mass m_{H} in assumption that the SM Higgs boson with this mass exists, as a function of the SM Higgs boson mass in the range 110–600 GeV (left) and 110–145 GeV (right). Expectations for the two subcombinations of fermionic and bosonic decay modes are shown. 
Exclusion limits on the SM Higgs boson
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The CL_{s} values for the SM Higgs boson hypothesis as a function of the Higgs boson mass. The observed values are shown by the solid line. The dashed line indicates the expected median of results for the background only hypothesis, while the green (dark) and yellow (light) bands indicate the ranges that are expected to contain 68% and 95% of all observed excursions from the median, respectively. The three horizontal lines on the CL_{s} plot show confidence levels of 90%, 95%, and 99%, defined as (1–CL_{s}). 

The 95% CL upper limits on the cross section ratio σ/σ_{SM} for the SM Higgs boson hypothesis as function of the Higgs boson mass. The observed values are shown by the solid line. The dashed line indicates the expected median of results for the background only hypothesis, while the green (dark) and yellow (light) bands indicate the ranges that are expected to contain 68% and 95% of all observed excursions from the median, respectively. 
Significance of the observed excess
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The observed local pvalue p_{0} for 7!TeV, 8!TeV data, and their combination as a function of the SM Higgs boson mass. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 

The observed local pvalue p_{0} for five subcombinations by decay mode and the overall combination as a function of the SM Higgs boson mass. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 

The observed local pvalue p_{0} for γgamma;, ZZ and their combination as a function of the SM Higgs boson mass. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 

The observed local pvalue p_{0} for γgamma;, ZZ, WW and their combination as a function of the SM Higgs boson mass. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 

The observed local pvalue p_{0} as a function of the SM Higgs boson mass, separately for searches with the 7 TeV and 8 TeV datasets. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 
Additional plots
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ZZ+γgamma;: The observed local pvalue p_{0} for 7!TeV, 8!TeV data, and their combination as a function of the SM Higgs boson mass, in decay modes with good mass resolution. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 

WW+bb+ττ: The observed local pvalue p_{0} for 7!TeV, 8!TeV data, and their combination as a function of the SM Higgs boson mass, in decay modes with poor mass resolution. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 

The observed local pvalue p_{0} for the subcombinations of high mass resolution channels, low mass resolution ones, and the overall combination as a function of the SM Higgs boson mass. The dashed lines show the expected local pvalue p_{0}(m_{H}), should a Higgs boson with a mass m_{H} exist. 
Mass of the observed state
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(Left) 2D 68% CL contours for a hypothesized Higgs boson mass m_{H} and signal strength σ/σ_{SM} for the untagged γγ, γγ with VBFlike dijet, and 4l, and their combination. In this combination, the relative signal strengths for the three final states are constrained by the expectations for the SM Higgs boson. (Right) 1D test statistics q(m_{H}) scan vs hypothesized Higgs boson mass m_{H} for the untagged γγ, γγ with VBFlike dijet, and 4l final states separately and for their combination. In this combination, signal strengths for the untagged γγ, gamma;γ with VBFlike dijet, and 4l final states are not constrained by the expectations for the SM Higgs boson. 
Additional plots
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1D test statistics q(m_{H}) scan vs hypothesized Higgs boson mass m_{H} for the combination of the high resolution channels. The dashed line shows the value of q(m_{H}) if all parameters except m_{H} are kept fixed at the values corresponding to the global best fit for m_{H}. In this combination, signal strengths for the untagged γγ, gamma;γ with VBFlike dijet, and 4l final states are not constrained by the expectations for the SM Higgs boson. The horizontal and vertical red lines denote the 68% and 95% CL intervals. 

2D test statistics –2 ln Q vs hypothesized Higgs boson mass m_{H} and signal strength σ/σ_{SM} for the combination of the high resolution channels. The cross indicates the bestfit values. The solid and dashed contours show the 68% and 95% CL ranges, respectively. In this combination, the relative signal strengths for the various final states are constrained by the expectations for the SM Higgs boson. 
Compatibility of the observed state with the SM Higgs boson hypothesis
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The observed bestfit signal strength μ̂ = σ/σ_{SM} as a function of the SM Higgs boson mass in the range 110–145 GeV. The bands correspond to the ±1σ uncertainties on the μ̂ values. 

The observed bestfit signal strength μ̂ = σ/σ_{SM} as a function of the SM Higgs boson mass for the 7 TeV and 8 TeV dataset separately, in the range 110–145 GeV. The bands correspond to the ±1σ uncertainties on the μ̂ values. 

The observed bestfit signal strength μ̂ = σ/σ_{SM} as a function of the SM Higgs boson mass for the 7 TeV and 8 TeV dataset separately, in the range 110–145 GeV. The bands correspond to the ±1σ uncertainties on the μ̂ values. 

Values of μ̂ = σ/σ_{SM} for the combination (solid vertical line) and for contributing channels (points). The vertical band shows the overall μ̂ value 0.80 ± 0.22. The horizontal bars indicate the ±1σ uncertainties on the μ̂ values for individual channels; they include both statistical and systematic uncertainties. 

Values of μ̂ = σ/σ_{SM} for the combination (solid vertical line) and for subcombinations grouped by decay mode (points). The vertical band shows the overall μ̂ value 0.80 ± 0.22. The horizontal bars indicate the ±1σ uncertainties on the μ̂ values for individual channels; they include both statistical and systematic uncertainties. 

Values of μ̂ = σ/σ_{SM} for the combination (solid vertical line) and for subcombinations grouped by a signature enhancing specific production mechanisms (points). The vertical band shows the overall μ̂ value 0.80 ± 0.22. The horizontal bars indicate the ±1σ uncertainties on the μ̂ values for individual channels; they include both statistical and systematic uncertainties. 

Values of μ̂ = σ/σ_{SM} for the combination and for contributing channels, for the 7 TeV and 8 TeV datasets separately. The horizontal bars indicate the ±1σ uncertainties on the μ̂ values; they include both statistical and systematic uncertainties. 

The 2Dscan of the test statistic –2 ln Q vs (c_{V}, c_{F}) parameters. The cross indicates the bestfit values. The solid and dashed contours show the 68% and 95% CL ranges, respectively. The diamond indicates the SM value (c_{V}, c_{F}) = (1,1). In this scan, the Higgs boson mass is assumed to be 125 GeV. 
Additional plots
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1D test statistics q(R_{W/Z}) scan vs the event rate modifier R_{W/Z}, profiling all other nuisances and the signal strength modifier μ_{ZZ}. The search channels included are the H→WW channel with zero jets and one jet in the final state, and the inclusive H→ZZ search. The horizontal and vertical red lines denote the 68% and 95% CL intervals. In this scan, the Higgs boson mass is assumed to be 125 GeV. 