Combination of Higgs Searches (December 2011)

This is a condensed description with plots for the analysis CMS-HIG-11-032

Abstract

The combination of results of searches for a Standard Model Higgs boson in five decay modes (γγ, bb, ττ, WW, and ZZ) performed by the CMS Collaboration at the Large Hadron Collider, CERN, is presented. The search is performed for Higgs boson masses in the range of 110-600 GeV/c². The data correspond to an integrated total luminosity of up to 4.7 fb-1 of proton-proton collisions at s = 7 TeV. The expected exclusion range in the absence of the Standard Model Higgs boson is 117-543 GeV/c² at 95% C.L. The observed data allow us to exclude the Standard Model Higgs boson in the mass range 127-600 GeV/c² at 95% C.L. At 99% C.L., we exclude the SM Higgs boson in the mass range from 128-525 GeV/c². The excess of events observed for hypothesised Higgs boson masses at the low end of the explored range makes the observed limits weaker than the expected ones. To ascertain the origin of this excess, more data are required.

Plots

Figure set Description Variants
The CLs value for the standard model Higgs hypothesis as a function of the Higgs boson mass in the range 110-600 GeV/c².
The observed values are shown by a solid line. The dashed black line indicates the median expected CLs value for the background-only hypothesis, while the green (yellow) bands indicate the ranges that are expected to contain 68% (95%) of all observed limit excursions from the median. The three red horizontal lines show confidence levels of 90%, 95%, and 99% defined as (1 - CLs).
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The combined 95% C.L. upper limits on the signal strength modifier μ = σ/σSM, as a function of the SM Higgs boson mass in the range 110-600 GeV/c².
The observed limits are shown by the solid symbols and the black line. The dashed line indicates the median expected limit on m for the background-only hypothesis, while the green (yellow) bands indicate the ranges that are expected to contain 68% (95%) of all observed limit excursions from the median.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The observed 95% C.L. upper limits on the signal strength modifier μ = σ/σSM, as a function of the SM Higgs boson mass in the range 110-600 GeV/c² as obtained with three methods.
CLs as presented in the note (black solid points and black solid line), CLs using an asymptotic approximation (red curve), and Bayesian (blue open circles and blue dashed line). The dashed line indicates the median expected limit on m for the background-only hypothesis, while the green (yellow) bands indicate the ranges that are expected to contain 68% (95%) of all observed limit excursions from the median, all computed for the CLs method as in the figure above.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The combined 95% C.L. upper limits on the signal strength modifier μ = σ/σSM, as a function of the SM Higgs boson mass in the range 110-600 GeV/c².
The observed limits are shown by the solid symbols and the black line. The dashed line indicates the median expected limit on m for the background-only hypothesis, while the green (yellow) bands indicate the ranges that are expected to contain 68% (95%) of all observed limit excursions from the median. The mass ranges excluded by LEP, by Tevatron and by this result are shown as hatched areas.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The combined 95% C.L. upper limits on the signal strength modifier μ = σ/σSM, as a function of the SM Higgs boson mass in the range 110-600 GeV/c².
The observed limits are shown by the solid symbols and the black line. The dashed line indicates the median expected limit on m for the background-only hypothesis, while the green (yellow) bands indicate the ranges that are expected to contain 68% (95%) of all observed limit excursions from the median. The mass ranges excluded by LEP is shown as hatched area. The observed (expected) limits from Tevatron are shown as a blue solid (dashed) line.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The observed 95% C.L. upper limits on the signal strength modifier μ = σ/σSM as a function of the SM Higgs boson mass in the range 110-600 GeV/c² for the five Higgs boson decay modes and their combination.
The limits are obtained with the asymptotic CLs method.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The 95% C.L. upper limits on the signal strength modifier μ = σ/σSM as a function of the SM Higgs boson mass in the range 110-600 GeV/c² for all eight analyses used in the combination. Solid lines are for observed limits, dashed for expected. The limits are obtained with the asymptotic CLs method. linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The expected 95% C.L. upper limits on the signal strength modifier μ = σ/σSM as a function of the SM Higgs boson mass in the range 110-600 GeV/c² for all eight analyses used in the combination.
The limits are obtained with the asymptotic CLs method.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The observed local p-value p0 (top panel) and best-fit signal strength μ̂ = σ/σSM (bottom panel) as a function of the SM Higgs boson mass.
The p-value is an estimated probability of upward background fluctuations as high or higher than the excesses observed in data. The μ̂ value indicates by what factor the SM Higgs cross section would have to be rescaled to best match the observed data.
The global significance of the observed excess (minimum local p-pvalue) in the low mass range 110-145 GeV/c² is about 1.9σ as estimated by generating multiple pseudo-data sets. The global significance of the observed excess in the full range 110-600 GeV/c² is about 0.6σ as estimated from the number of upcrossings at μ̂ = 0.
linear x(png, eps, pdf)
log x(png, eps, pdf)
low mass (png, eps, pdf)
low mass, square (png, eps, pdf)
The observed local p-value p0 as a function of the SM Higgs boson mass.
The solid black line is the combined result, while the color lines show results for individual channels. channels entering the combination vs. Higgs boson mass.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The observed local p-value p0 calculated in the asymptotic approximation (solid black line) and using pseudo-data (blue points).
The expected p-values at any given mass point, should a Standard Model Higgs boson exist with that mass, are shown with the dashed line.
low mass (png, eps, pdf)
The observed best-fit signal strength μ̂ = σ/σSM as a function of the SM Higgs boson mass. linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
Values of μ̂ = σ/σSM for the combination (solid vertical line) and contribution channels (points) for four hypothesized Higgs boson masses as indicated on the plot legends. The blue hatched band corresponds to the ±1σ errors on the overall μ̂ value. The red horizontal bars indicate the ±1σ on the μ̂ values for individual channels. 119.5 GeV/c²(png, eps, pdf)
124.0 GeV/c²(png, eps, pdf)
137.0 GeV/c²(png, eps, pdf)
144.0 GeV/c²(png, eps, pdf)
The global p-value to observe a minimum local p-value in the restricted mass range from 110 to 145 GeV/c². The global p-value is assessed by generating pseudo-data. png, eps, pdf
An example of a p-value scan obtained in one of the 500 pseudo-data sets. png, eps, pdf
95% C.L. upper limits on the signal strength modifier μ = σ/σSM, for the combination of the γγ and 4l analyses.
The limits are obtained with the asymptotic CLs method.
png, eps, pdf
95% C.L. upper limits on the signal strength modifier μ = σ/σSM, for the combination of the WW, bb and ττ analyses.
The limits are obtained with the asymptotic CLs method.
png, eps, pdf
The observed local p-value p0 (top panel) and best-fit signal strength μ̂ = σ/σSM (bottom panel) for the combination of the γγ and 4l analyses. png, eps, pdf
The observed local p-value p0 (top panel) and best-fit signal strength μ̂ = σ/σSM (bottom panel) for the combination of the WW, bb and ττ analyses. png, eps, pdf
The observed local p-value p0 calculated in the asymptotic approximation (solid black line) and using pseudo-data (blue points) for the combination of the γγ and 4l analyses.*
The expected p-values at any given mass point, should a Standard Model Higgs boson exist with that mass, are shown with the dashed line.
png, eps, pdf
The observed local p-value p0 calculated in the asymptotic approximation (solid black line) and using pseudo-data (blue points) for the combination of the WW, bb and ττ analyses.
The expected p-values at any given mass point, should a Standard Model Higgs boson exist with that mass, are shown with the dashed line.
png, eps, pdf
The observed local p-value p0 for the sub-combination γγ+4l and WW+bb+ττ and for the grand combination. png, eps, pdf

Tables

The following tables of raw numbers are also available as individual files in text format:

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Topic revision: r5 - 2011-12-16 - GiovanniPetrucciani
 
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