Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Advanced Analysis Methods for Higgs in Run II
Pushpa BhatFermilab
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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• Collaborators:– R. Gilmartin
– H. Prosper
– Run II SUSY/Higgs Working Group
P.B., R.G., H.P., PRD 62, 074022 (2000)
Run II Higgs Working Group Report,
hep-ph/0010338
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Outline
• Low mass Higgs MH < 130 GeV/c2
– WH, ZH Production
• Experimental Issues– Signal-background discrimination
– b-tagging
– Mass resolution
• Conclusions
bbbbbb ,,
bb
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Low Mass Higgs Study
• Signals:
• Channels:
bbEWHZHpp
bbZHpp
bbEWHpp
T
T
or:Etmissing
:leptondi
:lepton single
bbbbZH
bbWHpp
,
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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WH lbb Single Lepton Channel
• Signal– WH
• Backgrounds– Wbb– WZ– tqb– tb– Tt
• Detector Simulation– SHW
• Networks– Jetnet (v3.0)– 3 Networks/MH
• WH vs WZ• WH vs Wbb• WH vs tt
– 3 cuts
lT
T
bb
bT
bT
E
bbR
S
H
M
E
E
),( 21
2
1
(7,9,1)Network
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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WH(100 GeV/c2) vs. WbbVariables
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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WH(100 GeV/c2) NN Distributions
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Optimizing Cuts (WH100)
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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WH(110 GeV/c2) NN Distributions
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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NN Learning
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Discriminating Surface
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Standard vs. NN
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Combined Network
NN1WH-Wbb
NN2WH-WZ
NN3WH-top
NN4
NN4= f (NN1,NN2,NN3)
•Use in fitting distributions•Use in mass measurement
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Combined Network (WH110)
Currently see no improvement in significance by fitting the NN distributions for single lepton channel.This is work in progress
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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b-Tagging
• LEP experiments have impressive b-tagging using Neural Networks
• Use Neural Networks to combine lifetime and kinematic variables
• Work in progress at CDF & DØ – R. Demina
– S. Repond (ACAT2K Proceedings)
bottom charm primary
Points- single data, black - fit.
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Jet Energy Corrections
Correct jet energy using transverse energy and eta.
Use NN to fit the correction function
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Mass bb
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Higgs Mass Fits
S= 80 WH eventsWbb used as Background
S/B =1/10 Mfit =114 11 GeV/c2
S/B =1/5 Mfit =114 7 GeV/c2
Ref.: P.B., H.P. S.Snyder, PLB 407, 73 (1997)
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Work in Progress
• Systematic selection of variables• Continue study of b-tagging, mass
resolution• Fit distributions instead of counting
above cuts, and use new results in all channels
• Continue to develop Bayesian method for combining channels.
• Study effect of various systematic uncertainties on discovery reach.
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Conclusions
• Finding Higgs at the Tevatron will be extremely challenging!
• As evidenced from work at LEP, we will need all the sophistication in analysis that we can acquire.
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Back-up Slides
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Mbb
HT
Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat
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Higgs Mass Resolution
Use mjj and HT (= Etjets ) to train NNs to predict the Higgs
boson mass
13.8% 12.2%
13.1% 11..3%
13%13% 11%11%