Combined Upper Limit on Standard Model Higgs Boson Production at CDF for EPS 2011

The CDF Higgs Working Group

Links: CDF CDF's Higgs Results

Abstract
Documentation
(N)NLO Cross Section and Branching Ratio Table
Bayesian Framework
July 2011 Combined Results with up to 8.2 fb^-1
Summary Plots sorted by s/b
Projections
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Abstract

A combination of several searches for Standard Model Higgs boson production at CDF using a data sample up to 8.2 fb^-1 of integrated luminosity is performed. For m_H<125 GeV/c², the sensitivity-weighted average luminosity for the contributing channels is 7.5 fb^-1, and the main channels included for m_H>150 GeV/c² use a data sample corresponding to 8.2 fb^-1. The channels considered are WH→ lνbb, VH→METbb, ZH→l^-l⁺bb, H→γγ, VH→jjbb, H → W⁺W^-, H→&tau^-&tau⁺+2jets, H→ZZ→llll, two searches for ttH production, and a search for associated production of WH or ZH with a tau and two leptons. We calculate combined upper limits on the ratio of the Higgs boson cross section times the branching ratio to its Standard Model prediction (R₉₅) for Higgs boson masses between 100 and 200 GeV/c². The results are in good agreement with the expectations obtained from background-only pseudo-experiments. The 95% CL upper limits observed (expected) are factors of 1.55 (1.49) and 0.75 (0.79) times the Standard Model production cross sections for Higgs boson masses of 115 and 165 GeV/c², respectively. We exclude the ranges 156.5 < m_H < 173.7 GeV/c² and 100 < m_H < 104.5 GeV/c².

Documentation

July 2011 Public Note

Older Combinations

Documentation for Each Channel

WH→lνbb (2-jet, Neural Networks)	L=7.5 fb^-1	Web Page	Public note
WH→lνbb (3-jet, Matrix Elements)	L=5.6 fb^-1	Web Page	Public Note
VH→MET+bb	L=7.8 fb^-1	Web Page	Public Note
ZH→ll bb	L=7.5 fb^-1 (eebb) L=7.9 fb^-1 (μμbb)	Web Page	Public Note (ZH→eebb) Public Note (ZH→μμbb)
VH, VBF, ggH →2jet+H→ττ	L=6.0 fb^-1	Web Page	Public Note
VH,VBF →2jet+H→bb	L=4.0 fb^-1	Web Page	Public Note
H→γγ	L=7.0 fb^-1	Web Page	Public Note
gg→H→WW→lνlν	L=8.2 fb^-1 (W→e,μ+ν) L=8.2 fb^-1 (taus)	Web Page	Public Note (e, μ) Public Note (taus)
ttH(l+MET+jets)	L=7.5 fb^-1	Web Page	Public Note
ttH(No lepton)	L=5.7 fb^-1	Web Page	Public Note
H→ZZ→llll	L=8.2 fb^-1	Web Page	Public Note
VH→2τ+lepton	L=6.2 fb^-1	Web Page	Public Note

Cross Sections and Branching Ratios

We use the following references for our cross sections and branching ratios. The citations below include only those papers which contain numbers that we use. Further citations are available in our conference note.

The WH and ZH cross sections are from Baglio and Djouadi: arXiv:1003.4266v2, which is published as JHEP 1010:064 (2010). We have obtained from the authors an extension of Table 3 to include test mass range down to 100 GeV and predictions with more digits. The VBF production cross sections were computed with VBF@NNLO, and we multiply these by (1+δ_EW) from the HAWK program, which amounts to a roughly 2% to 3% downward correction.
The gg → H production cross section is calculated at NNLL in QCD and also includes two-loop electroweak effects. For details, see C. Anastasiou, R. Boughezal and F. Petriello, "Mixed QCD-electroweak corrections to Higgs boson production in gluon fusion", arXiv:0811.3458 [hep-ph] (2008), which is published as JHEP 0904:003 (2009), and D. de Florian and M. Grazzini, "Higgs production through gluon fusion: updated cross sections at the Tevatron and the LHC", arXiv:0901.2427v1 [hep-ph] (2009), which is published as Phys.Lett.B674:291-294 (2009). These cross were updated with the full m_top dependence in the calculation.
We follow the BNL Accord to assign scale uncertainties separately in the 0, 1, and 2 or more jet bins. Details can be found in arXiv:1107.2117.
PDF uncertainties follow the prescription of the PDF4LHC working group.
The Higgs boson decay branching ratios are those reported in the Handbook of LHC Cross Sections: 1. Inclusive observables, arXiv:1101.0593v2.
Higgs boson decay branching ratio uncertainties from m_b, m_c, and α_s are computed by Baglio and Djouadi in arXiv:1012.0530, which is published as JHEP 1103:055 (2011).

Bayesian Framework

The integrals over the uncertain parameters with their correlated priors from external constraints are done with a Markov Chain Monte Carlo integration method, using the Metropolis-Hastings algorithm.

Combination Results with up to 8.2 fb^-1 (July 2011)


The combined upper limit as a function of the Higgs boson mass between 100 and 200 GeV/c² Solid black: observed limit/SM; Dashed black: median expected limit/SM. Colored bands: +-1, 2 sigma distributions around median expected limit.	The combined upper limit as a function of the Higgs boson mass between 100 and 200 GeV/c². Solid lines indicate the observed upper limit for each channel and combined result (dark red). Dashed lines indicate the median expected upper limit for each channel and the combined result (dark red).

The summary table of observed and expected limits between 100 and 200 GeV/c² for the combination of all CDF Higgs search analyses. Limits are presented at the 95% CL.	Limits for the H→bb channels. They are: lvbb, METbb, llbb, jjbb, and ttH. Limits are presented at the 95% CL.

Events Ranked by s/b


Events in all search channels, sorted by the s/b in the bins in which they are found. Signal and background totals are shown, stacked. This plot is shown for m_H=100 GeV/c²	Cumulative distributions of background, data and signal+background. The s/b distribution is integrated from the high s/b side downwards. This plot is shown for m_H=100 GeV/c²

Events in all search channels, sorted by the s/b in the bins in which they are found. Signal and background totals are shown, stacked. This plot is shown for m_H=115 GeV/c²	Cumulative distributions of background, data and signal+background. The s/b distribution is integrated from the high s/b side downwards. This plot is shown for m_H=115 GeV/c²

Events in all search channels, sorted by the s/b in the bins in which they are found. Signal and background totals are shown, stacked. This plot is shown for m_H=150 GeV/c²	Cumulative distributions of background, data and signal+background. The s/b distribution is integrated from the high s/b side downwards. This plot is shown for m_H=150 GeV/c²

Events in all search channels, sorted by the s/b in the bins in which they are found. Signal and background totals are shown, stacked. This plot is shown for m_H=165 GeV/c²	Cumulative distributions of background, data and signal+background. The s/b distribution is integrated from the high s/b side downwards. This plot is shown for m_H=165 GeV/c²

Background-subtracted data distributions for events in all channels, sorted and collected by s/b. The background is fit to the data. The error bars on the background-subtracted data points are the square roots of the best-fit background rates in those bins. The blue histograms show the remaining uncertainty on the background rates after the fit. The shaded histogram shows the expected signal yield for a 115 GeV/c² Higgs boson.	Background-subtracted data distributions for events in all channels, sorted and collected by s/b. The background is fit to the data. The error bars on the background-subtracted data points are the square roots of the best-fit background rates in those bins. The blue histograms show the remaining uncertainty on the background rates after the fit. The shaded histogram shows the expected signal yield for a 165 GeV/c² Higgs boson.

Projections

Achieved and projected median expected upper limits on the SM Higgs boson cross section, by date. The solid lines are 1/sqrt(L) projections. The top of the orange band corresponds to the Summer 2007 performance expected limit divided by 1.5, and the bottom of the orange band corresponds to the Summer 2007 performance expected limit divided by 2.25. The luminosity for the July 2011 point is 5.6 fb^-1, a sensitivity-weighted average of the contributing channels' analyzed luminosities. These plots are shown for m_H=115 GeV/c².

Achieved and projected median expected upper limits on the SM Higgs boson cross section, by date. The solid lines are 1/sqrt(L) projections. The top of the orange band corresponds to the Summer 2007 performance expected limit divided by 1.5, and the bottom of the orange band corresponds to the Summer 2007 performance expected limit divided by 2.25. This plot is shown for m_H=160 GeV/c². The luminosity for the July 2011 point is 5.9 fb^-1.

2xCDF Projections

For current D0 Higgs Search Results and Performance, please visit D0's Higgs Results Web Page.

Projected median expected upper limits on the SM Higgs boson cross section, scaling CDF performance to twice the luminosity. The solid lines are 1/sqrt(L) projections, as functions of integrated luminosity per experiment. The top of the orange band corresponds to the Summer 2007 performance expected limit divided by 1.5, and the bottom of the orange band corresponds to the Summer 2007 performance expected limit divided by 2.25. This plot is shown for m_H=115 GeV/c² Projected median expected upper limits on the SM Higgs boson cross section, scaling CDF performance to twice the luminosity. The solid lines are 1/sqrt(L) projections, as functions of integrated luminosity per experiment. The top of the orange band corresponds to the Summer 2007 performance expected limit divided by 1.5, and the bottom of the orange band corresponds to the Summer 2007 performance expected limit divided by 2.25. This plot is shown for m_H=160 GeV/c²

Probability of seeing a 2σ excess as a function of m_H for analyzed integrated luminosities of 5 fb^-1 and 10 fb^-1 per experiment, assuming CDF and D0 perform the same. Two scenarios are shown, in which channels have the same performance as for the Winter 2009 combination (solid lines), and for the case with another factor of 1.5 in the sensitivity (dashed lines). The current observations are not taken into account, only expected sensitivities are shown. Sensitivities are expected to scale with sqrt(L). Probability of seeing a 3σ excess as a function of m_H for analyzed integrated luminosities of 5 fb^-1 and 10 fb^-1 per experiment, assuming CDF and D0 perform the same. Two scenarios are shown, in which channels have the same performance as for the Winter 2009 combination (solid lines), and for the case with another factor of 1.5 in the sensitivity (dashed lines). The current observations are not taken into account, only expected sensitivities are shown. Sensitivities are expected to scale with sqrt(L).

Experimental Contacts

If you wish to present this material publicly or would like further information, please email the CDF combination group and conveners

Doug Benjamin    dbenjamin  AT fnal.gov
Matt Herndon     herndon    AT hep.wisc.edu
Eric James       jameseb    AT fnal.gov
Tom Junk         trj        AT fnal.gov
Ben Kilminster   bjk        AT fnal.gov
Nils Krumnack    nils       AT fnal.gov
Weiming Yao      wmyao      AT lbl.gov

July 2011, CDF Higgs Discovery Group


Projected median expected upper limits on the SM Higgs boson cross section, scaling CDF performance to twice the luminosity. The solid lines are 1/sqrt(L) projections, as functions of integrated luminosity per experiment. The top of the orange band corresponds to the Summer 2007 performance expected limit divided by 1.5, and the bottom of the orange band corresponds to the Summer 2007 performance expected limit divided by 2.25. This plot is shown for m_H=115 GeV/c²	Projected median expected upper limits on the SM Higgs boson cross section, scaling CDF performance to twice the luminosity. The solid lines are 1/sqrt(L) projections, as functions of integrated luminosity per experiment. The top of the orange band corresponds to the Summer 2007 performance expected limit divided by 1.5, and the bottom of the orange band corresponds to the Summer 2007 performance expected limit divided by 2.25. This plot is shown for m_H=160 GeV/c²

Probability of seeing a 2σ excess as a function of m_H for analyzed integrated luminosities of 5 fb^-1 and 10 fb^-1 per experiment, assuming CDF and D0 perform the same. Two scenarios are shown, in which channels have the same performance as for the Winter 2009 combination (solid lines), and for the case with another factor of 1.5 in the sensitivity (dashed lines). The current observations are not taken into account, only expected sensitivities are shown. Sensitivities are expected to scale with sqrt(L).	Probability of seeing a 3σ excess as a function of m_H for analyzed integrated luminosities of 5 fb^-1 and 10 fb^-1 per experiment, assuming CDF and D0 perform the same. Two scenarios are shown, in which channels have the same performance as for the Winter 2009 combination (solid lines), and for the case with another factor of 1.5 in the sensitivity (dashed lines). The current observations are not taken into account, only expected sensitivities are shown. Sensitivities are expected to scale with sqrt(L).