Combination of Higgs Searches (EPS 2011)

This is a condensed description with plots for the analysis LINK TO CDS

Abstract

The overall combination is presented of eight standard model (SM) Higgs boson searches performed by the CMS Collaboration using the following Higgs boson decay signatures: H → γγ, H → ττ, H → WW → 2l2ν, H → ZZ → 4l, H → ZZ → 2l2ν, and H → ZZ → 2l2q. Depending on the analysis, the amount of data used corresponds to 1.0-1.1 fb−1 of integrated luminosity. The SM Higgs boson is excluded at 95% C.L. in two mass ranges 149-206 and 300-440 GeV/c², as well as several narrower intervals in between. The expected exclusion in the absence of a signal is 127-420 GeV/c². At 90% C.L., we exclude the SM Higgs boson in the continuous mass range from 145-480 GeV/c². The same experimental search results, reinterpreted in the context of the standard model with 4 fermion generations (SM4), allow us to exclude the SM4 Higgs boson with a mass in the range 120-600 GeV/c² at 95% C.L.

Plots for SM Higgs Boson

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 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 observed limits inferred from the Bayesian approach are shown as open circles. 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. Both bands and the median are shown for the CLs method.
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 observed limits inferred from the Bayesian approach are shown as open circles. 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. Both bands and the median are shown for the CLs method. The mass ranges excluded by LEP and by Tevatron are shown as hatched areas.
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 six major analyses and their combination.
The limits are obtained with the CLs method.
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)
The observed best-fit signal strength μ̂ = σ/σSM (top) and an estimate of local p-values (bottom) vs Higgs boson mass.
The p-value is an estimated probability of upward background fluctuations as high or higher than the excesses observed in data. It has to be further de-rated by the trial factor of a yet undetermined scale (analyses used in the combination have been shown to have the trial factors ranging from O(1)-O(100)). The μ̂ value indicates by what factor the SM Higgs cross section would have to be rescaled to best match the observed data.
png, eps, pdf
The overall combined local p-values (solid black line) and contributions of individual channels entering the combination vs. Higgs boson mass.
The p-value is an estimated probability of upward background fluctuation as high or higher than the excesses observed in data. It has to be further de-rated by the trial factor of a yet undetermined scale (analyses used in the combination have been shown to have the trial factors ranging from O(1)-O(100))
linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)

Plots for SM4 Higgs Boson

The plots below refer to the searches for a Higgs boson in the context of the standard model model with four generations of fermions.
Figure set Description Variants
*The combined 95% C.L. upper limits on the signal strength modifier μ = σ/σSM4, as a function of the SM4 Higgs boson mass in the range 110-600 GeV/c². The observed CLs-based limits are shown by the solid symbols and black line and exclude the SM4 Higgs with a mass from 120 GeV/c² to 600 GeV/c² (maximum Higgs boson mass covered by the current analyses). The Bayesian limits are shown with open symbolds and give nearly identical results. Both bands and the median are shown for the CLs method. linear x (png, eps, pdf)
log x (png, eps, pdf)
low mass (png, eps, pdf)

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Topic revision: r1 - 2011-08-24 - AndreyKorytov
 
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