1Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

Higgs Searches with 1 fb-1

Per JonssonImperial College London

On behalf of the Higgs Group

D-Zero Workshop, Vancouver13-18 June 2005

2Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

Outline• Status/plans for 1 fb-1

of data:– Muons/Electrons:

• W/Z + jets• WH->lbb• H->WW(*)

• ZH->llbb

– Jets:• Z->bb• ZH->bb• bbh->bbbb

– Higgs searches with ‘s• Summary

3Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

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.

4Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

WH->lbb &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

5Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

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

6Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

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

7Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

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

8Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

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 tanfor mH = 90

GeV

9Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

Higgs Searches with ‘s• bb(h/H/A) bb bblhad

– A. Goussiou, Y. Pogorelov, P. Svoisky– Plan on p14 pass2 publ. end of 2005 – Then p17 analysis

• bb bbhadhad– 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

pre-TAUOLA fix post-TAUOLA fix

Polarization in p14 TAUOLA was wrong

MC samples must be regenerated w. p17: high priority

10Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

TriggersHiggs 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

11Plenary Physics Meeting,

17 June 05

Per JonssonImperial College London

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