Combined results of searches for the standard model Higgs boson in pp collisions at sqrt(s) = 7 TeV (February 2012)

This is a condensed description with plots for the analysis CMS-HIG-11-032, as submitted to arXiv:1202.1488 and PLB.

Abstract

Combined results are reported from searches for the standard model Higgs boson in proton-proton collisions at s = 7 TeV in five Higgs boson decay modes: γγ, bb, ττ, WW, and ZZ. The explored Higgs boson mass range is 110–600 GeV. The analysed data correspond to an integrated luminosity of 4.6–4.8 fb–1. The expected excluded mass range in the absence of the standard model Higgs boson is 118–543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127–600 GeV at 95% CL, and in the mass range 129–525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1 σ, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance greater than 3.1 σ anywhere in the search range 110–600 (110–145) GeV is estimated to be 1.5 σ (2.1 σ). More data are required to ascertain the origin of this excess.

Full set of plots

CMS Combination

Plot Caption
The CLs 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 CLs plot show confidence levels of 90%, 95%, and 99%, defined as (1–CLs).
The 95% CL upper limits on the signal strength parameter μ = σ/σSM 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.
The 95% CL upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass as obtained with three methods. CLs as presented in the paper (black solid points and black solid line), CLs using an asymptotic approximation (red curve), and Bayesian (blue open circles and blue dashed line). 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, all computed for the CLs method as presented in the paper.
The observed local p-value p0 as a function of the SM Higgs boson mass in the range 110–145 GeV. The global significance of the observed maximum excess (minimum local p-value) in this mass range is about 2.1σ, estimated using pseudoexperiments. The dashed line on the plot shows the expected local p-values p0(mH), should a Higgs boson with a mass mH exist.
The observed best-fit signal strength μ̂ = σ/σSM as a function of the SM Higgs boson mass. The band in the plot corresponds to the ±1σ uncertainties on the μ̂ values.

Summary plots with all the individual search channels

Plot Caption
The 95% CL observed upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual search channels. The limits are obtained with the asymptotic CLs approximation.
(version with solid lines for all channels)
The 95% CL observed upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual search channels. The limits are obtained with the asymptotic CLs approximation.
(alternate version with different line styles)
The 95% CL upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual search channels. Observed limits are shown with solid lines, while expected limits are shown with dashed lines. The limits are obtained with the asymptotic CLs approximation.
The 95% CL expected upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual search channels. The limits are obtained with the asymptotic CLs approximation.
(version with solid lines)
The 95% CL expected upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual search channels. The limits are obtained with the asymptotic CLs approximation.
(alternate version with dashed lines)
The observed local p-value p0 as a function of the SM Higgs boson mass in the range 110–145 GeV, for the full combination and the individual search channels. The global significance of the observed maximum excess (minimum local p-value) for the full combination in this mass range is about 2.1σ, estimated using pseudoexperiments. The dashed line on the left plot shows the expected local p-values p0(mH) for the combination, should a Higgs boson with a mass mH exist.

Summary plots by decay mode (all ZZ searches are combined)

Plot Caption
The 95% CL observed upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual decay modes. The limits are obtained with the asymptotic CLs approximation.
(version with solid lines for all channels)
The 95% CL observed upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual decay modes. The limits are obtained with the asymptotic CLs approximation.
(alternate version with different line styles)
The 95% CL upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual decay modes. Observed limits are shown with solid lines, while expected limits are shown with dashed lines. The limits are obtained with the asymptotic CLs approximation.
The 95% CL expected upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual decay modes. The limits are obtained with the asymptotic CLs approximation.
(version with solid lines)
The 95% CL expected upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the individual decay modes. The limits are obtained with the asymptotic CLs approximation.
(alternate version with dashed lines)
The observed local p-value p0 as a function of the SM Higgs boson mass in the range 110–145 GeV, for the full combination and the individual decay modes. The global significance of the observed maximum excess (minimum local p-value) for the full combination in this mass range is about 2.1σ, estimated using pseudoexperiments. The dashed line on the left plot shows the expected local p-values p0(mH) for the combination, should a Higgs boson with a mass mH exist.

Plots of the separate combinations of ZZ+γγ and bb+ττ+WW

Plot Caption
The 95% CL upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the ZZ+γγ (left) and bb+ττ+WW (right) sub-combinations. 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 limits are obtained with the asymptotic CLs approximation.
The 95% CL upper limits on the signal strength parameter μ = σ/σSM for the SM Higgs boson hypothesis as function of the Higgs boson mass, for the full combination and the two sub-combinations. Observed limits are shown with solid lines, while expected limits are shown with dashed lines. The limits are obtained with the asymptotic CLs approximation.
The observed local p-value p0 as a function of the SM Higgs boson mass in the range 110–145 GeV, for the full combination and the two sub-combinations. The global significance of the observed maximum excess (minimum local p-value) for the full combination in this mass range is about 2.1σ, estimated using pseudoexperiments. The dashed line on the left plot shows the expected local p-values p0(mH) for the combination, should a Higgs boson with a mass mH exist.
The observed best-fit signal strength μ̂ = σ/σSM as a function of the SM Higgs boson mass in the range 110–145 GeV, for the ZZ+γγ (left) and bb+ττ+WW (right) sub-combinations. The band in the plot corresponds to the ±1σ uncertainties on the μ̂ values.

Channel compatibility plots

Plot Caption
Values of μ̂ = σ/σSM for the combination (solid vertical line) and for contributing channels (points), for a hypothesized Higgs boson mass of 119.5 GeV. The band corresponds to ±1σ uncertainties on the overall μ̂ value. The horizontal bars indicate ±1σ uncertainties on the μ̂ values for individual channels.
Values of μ̂ = σ/σSM for the combination (solid vertical line) and for contributing channels (points), for a hypothesized Higgs boson mass of 124 GeV. The band corresponds to ±1σ uncertainties on the overall μ̂ value. The horizontal bars indicate ±1σ uncertainties on the μ̂ values for individual channels.
Values of μ̂ = σ/σSM for the combination (solid vertical line) and for contributing channels (points), for a hypothesized Higgs boson mass of 137 GeV. The band corresponds to ±1σ uncertainties on the overall μ̂ value. The horizontal bars indicate ±1σ uncertainties on the μ̂ values for individual channels.
Values of μ̂ = σ/σSM for the combination (solid vertical line) and for contributing channels (points), for a hypothesized Higgs boson mass of 144 GeV. The band corresponds to ±1σ uncertainties on the overall μ̂ value. The horizontal bars indicate ±1σ uncertainties on the μ̂ values for individual channels.

Exclusion limits compared to LEP, Tevatron

Plot Caption
The 95% CL upper limits on the signal strength parameter μ = σ/σSM 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. The mass ranges first excluded by LEP and Tevatron are shown as hatched areas.
The 95% CL upper limits on the signal strength parameter μ = σ/σSM 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. The mass ranges first excluded by LEP, Tevatron and this measurement are shown as hatched areas.
The 95% CL upper limits on the signal strength parameter μ = σ/σSM 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. The mass range excluded by LEP is shown as hatched area. The observed (expected) limits from Tevatron are shown as a blue solid (dashed) line
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Topic revision: r6 - 2012-03-09 - GiovanniPetrucciani
 
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