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Advanced Analysis Methods for Higgs in Run II

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Advanced Analysis Methods for Higgs in Run II Pushpa Bhat Fermilab Collaborators: R. Gilmartin H. Prosper Run II SUSY/Higgs Working Group P.B., R.G., H.P., PRD 62 ... – PowerPoint PPT presentation

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Title: Advanced Analysis Methods for Higgs in Run II


1
Advanced Analysis Methods for Higgs in Run II
  • Pushpa Bhat
  • Fermilab

2
  • 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
  • For a discussion of Advanced Methods, see
  • my video-streamed plenary talk at
  • http//conferences.fnal.gov/acat2000/

3
Outline
  • Low mass Higgs MH lt 130 GeV/c2
  • WH, ZH Production
  • Experimental Issues
  • Signal-background discrimination
  • b-tagging
  • Mass resolution
  • Conclusions

4
Low Mass Higgs Study
  • Signals
  • Channels

5
WH ? l?bb Single Lepton
Channel
  • Signal
  • WH
  • Backgrounds
  • Wbb
  • WZ
  • tqb
  • tb
  • ttbar
  • Detector Simulation
  • SHW
  • Networks
  • Jetnet (v3.0)
  • 3 Networks/MH
  • WH vs WZ
  • WH vs Wbb
  • WH vs tt
  • 3 cuts

(7,9,1) Network
6
WH(100 GeV/c2) vs. Wbb Variables
7
WH(100 GeV/c2) vs. WZ Variables
8
WH(100 GeV/c2) NN Distributions
9
Optimizing Cuts (WH100)
10
WH(110 GeV/c2) NN Distributions
11
NN Learning
12
Discriminating Surface
13
Standard vs. NN
14
Combined Network
NN1 WH-Wbb
NN2 WH-WZ
NN4
NN3 WH-top
NN4 f (NN1,NN2,NN3)
  • Use in fitting distributions
  • Use in mass measurement

15
Combined Network (WH110)
Currently see no improvement in significance by
fitting the NN distributions for single lepton
channel. This is work in progress
16
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 60 better effpurity than
    conventional
  • S. Repond (ACAT2K Proceedings)

P
b
b jets
Non-b jets
Channel-dependent b-tagging
17
Jet Energy Corrections
Example
Correct jet energy using transverse energy and
eta.
Use NN to fit the correction function
?
18
Mass
Another approach Find the parameters for energy
correction by minimizing the variance in Mbb
directly
19
Higgs Mass Fits
S 80 WH events Wbb used as Background
S/B 1/10 Mfit 114 ?11 GeV/c2 S/B 1/5 Mfit
114 ? 7 GeV/c2
MethodP.B., H.P., S.Snyder, PLB 407, 73 (1997)
20
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.

21
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.

22
Back-up Slides
23
Mbb
HT
24
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
11
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