Advanced Analysis Methods for Higgs in Run II

transcript

Future of Higgs Physics Workshop May 3-5, 2001 Pushpa Bhat

Pushpa BhatFermilab

• 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

Outline

• Low mass Higgs MH < 130 GeV/c2

– WH, ZH Production

• Experimental Issues– Signal-background discrimination

– b-tagging

– Mass resolution

• Conclusions

bbbbbb ,,

Low Mass Higgs Study

• Signals:

• Channels:

bbEWHZHpp

bbZHpp

bbEWHpp

or:Etmissing

:leptondi

:lepton single

bbbbZH

bbWHpp

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

),( 21

(7,9,1)Network

WH(100 GeV/c2) vs. WbbVariables

WH(100 GeV/c2) NN Distributions

Optimizing Cuts (WH100)

WH(110 GeV/c2) NN Distributions

NN Learning

Discriminating Surface

Standard vs. NN

Combined Network

NN1WH-Wbb

NN2WH-WZ

NN3WH-top

NN4= f (NN1,NN2,NN3)

•Use in fitting distributions•Use in mass measurement

Combined Network (WH110)

Currently see no improvement in significance by fitting the NN distributions for single lepton channel.This is work in progress

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.

Jet Energy Corrections

Correct jet energy using transverse energy and eta.

Use NN to fit the correction function

Mass bb

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)

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.

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.

Back-up Slides

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%

Advanced Analysis Methods for Higgs in Run II

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