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Tevatron Combination of SM Higgs Searches and Fourth Generation Limits Satish Desai Fermilab For the CDF and D Collaborations 19 th International Conference on Supersymmetry and Unification Of Fundamental Interactions Fits and

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Tevatron Combination of SM Higgs Searches and Fourth Generation Limits

Satish Desai – Fermilab For the CDF and DØ Collaborations 19th International Conference on Supersymmetry and Unification Of Fundamental Interactions

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Tevatron Combined SM and 4th Gen Higgs Limits 2

Fits and Constraints

MH < 158 GeV (indirect constraints) MH < 185 GeV (include LEP search)

Electroweak symmetry

breaking is a cornerstone

f the standard model
Higgs mechanism provides

mass for the W and Z

A consequence of this is

the Higgs boson

Mass is not predicted

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Tevatron Combined SM and 4th Gen Higgs Limits 3

10.4 fb-1 Delivered Recorded 11.7 fb-1 Today: Up to 8.6 fb-1

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Tevatron Combined SM and 4th Gen Higgs Limits 4

Higgs Production and Decay

For MH <≈ 135 GeV,

H → bb dominates

Control bg with leptons

from associated W/Z

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Tevatron Combined SM and 4th Gen Higgs Limits 5

Higgs Production and Decay

For MH >≈ 135 GeV,

H → WW dominates

Control bg with leptons

from W decays

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Tevatron Combined SM and 4th Gen Higgs Limits 6

Leave No Higgs Behind

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Tevatron Combined SM and 4th Gen Higgs Limits 7

Leave No Higgs Behind

Many different channels from both CDF and DØ For more details, see talks by

X. Bu, G. Facini,
S. Shalhout, R. Nayyar

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Tevatron Combined SM and 4th Gen Higgs Limits 8

Searching for H → WW (example)

Exploit low S/B regions without

diluting more senstive subsamples

Selection defined by final state
Train multivariate discriminants

to extract more sensitvity

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Tevatron Combined SM and 4th Gen Higgs Limits 9

Combined Discriminants

MH: 115 GeV

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Tevatron Combined SM and 4th Gen Higgs Limits 10

Combined Discriminants

MH: 165 GeV

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Tevatron Combined SM and 4th Gen Higgs Limits 11

Systematic Uncertainties

Limits extracted using shape

comparisons of final discriminant

Important to consider
Normalization uncertainties
Shape uncertainties
Track correlations across

channel and experiment

Source Size Trigger 2% Jet Energy Scale 1-3% Jet Identification 2% Multijet Estimate 0-25% b-tagging Efficiency 1-6% Luminosity 6% Cross Sections 6-20%

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Tevatron Combined SM and 4th Gen Higgs Limits 12

Getting the Results

∏ Poisson(xi∣Bi(θ)+RS (θ))

bins i

Bayesian Method

0.95=∫0

limit dR∫ L(RS ,B , x ,θ)d θ

∫0

∞ dR∫ L(RS , B , x ,θ)d θ

Use Bayesian method
Use CLs as cross check
Agree within 2% on average (at

worst 10% depending on MH)

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Tevatron Combined SM and 4th Gen Higgs Limits 13

The Log Likelihood Ratio

LLR from CLs method

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Tevatron Combined SM and 4th Gen Higgs Limits 14

Limits

Excluded Regions: Observed: 100-109 and 156-177 GeV Expected: 100-108 and 148-181 GeV

Limits at MH =115 GeV: Observed: 1.16 SM Expected: 1.17 SM

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Fourth Generation Models

Additional quark loops enhance

(gg→H) by factor of 9

Higgs mass up to 300 GeV

allowed by indirect constraints

Two scenarios based
n mass of extra

leptons

Low mass exclusion:

124 – 286 GeV

High mass exclusion:

124 – 300 GeV

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Looking to the Future

Already recorded more than 10 fb-1

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Summary

We already exclude a significant part of the MH

range allowed by electroweak fits

Tevatron reaching sensitivity in dominant decay

modes in the most interesting region

Look forward to an exciting set of results in 2012

http://www-d0.fnal.gov/Run2Physics/WWW/results/higgs.htm http://www-cdf.fnal.gov/physics/new/hdg/hdg.html

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Tevatron Combined SM and 4th Gen Higgs Limits 18

Summary

We already exclude a significant part of the MH

range allowed by electroweak fits

Tevatron reaching sensitivity in dominant decay

modes in the most interesting region

Look forward to an exciting set of results in 2012

http://www-d0.fnal.gov/Run2Physics/WWW/results/higgs.htm http://www-cdf.fnal.gov/physics/new/hdg/hdg.html

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Backup Slides

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Between the High and the Low

High mass channels from Moriond 2011 H → bb channels from EPS 2011

Sensitivity at MH = 135 GeV: 2.2  SM Sensitivity at MH = 135 GeV: 2.?  SM

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The Big Picture

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1-CLs

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