# Presentation: 716594

## Higgs Searches with 1 fb-1

**Per Jonsson**
**Imperial College London**
**On behalf of**
** ****the Higgs Group**

**D-Zero Workshop, Vancouver**
**13-18 June 2005**
** **

## Outline

- Status/plans for 1 fb-1 of data:
- Muons/Electrons:
- W/Z + jets
- WH->lbb
- H->WW(*)
- ZH->llbb
- Jets:
- Z->bb
- ZH->bb
- bbh->bbbb
- Higgs searches with ‘s
- Summary

## W/Z+jets (G.Hesketh, T.Nunneman, B.Tiller)

- Test of QCD but also main background to many Higgs searches
- “First generation” analysis of
-      Z->ee + jets to be published w. p14 data
- Plan to cover both electron and muon channels of W/Z w. p17 data:
- Developing all analysis in CAF
- Understanding of p17 jets limiting factor
- p14 results for Moriond
- Preliminary result w. p17 for
-     next summer

- Z-> incl. jet mult.

## WH->lbb &TC (G.Bernardi, H.Kim, L.Sonnenschein, S.Trincaz-Duvoid, J.Yu, L.Feligioni, M.Narain, S.Desai, J.Hobbs)

- New WH results:
- 382 inv. pb (electron channel)
- Wbb limit: 4.6pb vs. 6.6pb published with 174pb^-1
- 371 inv. pb (muon channel)
- Wbb limit: 4.1pb
- Goals:
- WH analyses e + mu
-      channel preliminary combination for EPS
- Technicolor publications
-      on Pass2 data
- Measure Wbb (e channel) w.
-     1 fb-1 :
- Gain ~10% sensitivity w.
-      looser b-tag
- Also expect gain from
-     b-JES, tau channel, NN

- e channel

- mu channel

## H->WW(*) & ZH->llbb (Q.Li, J.Elmshauser, M.Hohlfeld, M.Titov, J.Heinmiller, N.Varelas, Y.Mutaf, H.Dong)

- H->WW(*)
- PRL draft based on 300-325 pb-1 under EB review
- New p17 analysis to start soon
- Expect improvements from:
- Advanced analysis techniques
- Lepton ID and  muon resolution
- Bkg understanding
- ZH->llbb plans for 1fb-1:
- Z + b-jet cross section
- Z + b/Z + j measurement
- Z + bb and ZH cross section limits
- Improvements (ZH->bb):
- Looser b-tag: x2.4
- Muon isolation:x1.5
- Start p17 analysis w. CAF in Sept.

- ZH->bb: Improved sensitivity w.
- x-loose JLIP and opt. muon isolation

## Z->bb (P.Jonsson, A.Jenkins, G.Davies, A.Haas, C.Johnson)

- Important for b-jet energy scale, light Higgs searches, bb mass resolution, b-tagging
- p14 Pass2 analysis w. note in preparation:
- aim to complete analysis for publication
- then on to p17 analysis:
- Expect ~1400 Z->bb events w. 1 fb-1

**Observe ~420 +/- 145 events**
**Systematic errors being worked on **

**v12 Data**
**Signal MC**

## ZH->bb (M.Petteni, M.Tomoto)

- First results shown at Moriond ‘04:
- V12, pass1 data, 261 pb-1
- Working on improved pass2 analysis:
- Looser b-tags, QCD cuts
- x2 Increased sensitivity
- Publish as soon as possible
- Then move on to p17 analysis with CAF:
- Room for improvement of analysis:
- Hadronic calibration expected to have large impact
- Aiming for Moriond ’05:
- Tight schedule with p17 JES/BID availability

- Major limitation of current analysis is L1 trigger acceptance: RunIIb trigger upgrade will bring significant improvement

## bb(h/H/A)->bbbb (M.Michaut, B.Tuchming, A. Haas, T.Scanlon, J.Rani, A.Kharchilava)

- Pass1 p14 analysis (260 pb-1) submitted to PRL
- Almost set up to start p17 analysis:
- Switch to CAF by July
- Ready with full 1 fb-1 analysis for Moriond
- Expected improvements to the analysis:
- Neural Network b-tagger:
- 20% eff.== +107% luminosity
- SL tagger
- Jet energy resolution:
- Cal-track jet:
- 15% less bkg. == + 18% luminosity
- Better JES
- Low pT jet reco/ID efficiency
- Lower jet pT Threshold in p17 (8 GeV -> 6 GeV)
- Opt. jet reconstruction alg. for low pT
- Smaller uncertainties
- Add more triggers and topological variabels
- In total expect improved reach from:
- tan> 60 to tanfor mH = 90 GeV

## Higgs Searches with ‘s

- bb(h/H/A)  bb  bblhad
- A. Goussiou, Y. Pogorelov, P. Svoisky
- Plan on p14 pass2 publ. end of 2005
- Then p17 analysis
- bb  bbhadhad
- Y. Hu
- p14 results for winter 2006
- Then extend to p17
- H    had
- S. Kelly, M. Owen, S. Soldner-Rembold
- P14 pass2 analysis just starting
- Prel. results winter  2006
- Charged Higgs
- A. Pompos, A. Sopzac
- H++H- -    :  marginal w/ 1fb-1
- M. Owen, S. Soldner-Rembold

- Polarization in p14 TAUOLA was wrong

- MC samples must be regenerated w. p17:
-              high priority

## Triggers

- _Higgs trigger concerns:_
-  - Risk of getting Higgs triggers prescaled at high luminosities
- _mu+jet special concern_
- _Need low pT efficiency_
- - New set of triggers in v14
- - New purely track/muon based ZBB triggers at L1/L2
-    ~ STT IP tracks at L2
-    ~ L3 filters for both W/ZH and
-        Z->bb
- Newly designed single and di-tau triggers
-    ~ Hope to run them unprescaled to high luminosities

- Example: WH(bb) analysis:

- Large gain in combining single muon and mu+jet triggers. Adding Higgs triggers results in further gain of about 14% in v13

## Summary

- Moving all Higgs analyses to p17, CAF and the 1 fb-1 dataset:
- Aim to deliver quick results short time after data available
- Tau analyses are starting to become an important part of the Higgs searches at D0
- We hope to contribute to more efficient triggers at RunIIb
- Combination effort of SM searches are about to start