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Higgs Searches at Tevatron Stéphanie Beauceron LPNHE - Paris on behalf of CDF and DØ Collaborations. Thanks to everybody for their contribution to this talk. Outline. Chicago .  p. p. 1.96 TeV. Booster. p. CDF. DØ. Tevatron.  p. p sou rce. Main Injector & Recycler.

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Higgs Searches at Tevatron Stéphanie Beauceron LPNHE - Paris

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Higgs searches at tevatron st phanie beauceron lpnhe paris

Higgs Searches at

Tevatron

Stéphanie Beauceron

LPNHE - Paris

on behalf of CDF and DØ Collaborations

Thanks to everybody for their contribution to this talk

Stephanie Beauceron - LPNHE Paris VI et VII


Outline

Outline

Chicago

p

p

1.96 TeV

Booster

p

CDF

Tevatron

p

p source

Main Injector

& Recycler

  • Standard Model Higgs

  • Higgs Beyond the Standard Model

  • limits on Wbb/WH production

  • (Z+b)/(Z+j) ratio

  • limits on HWW(*)l+l- production

  • limits on neutral Higgs at high tanβ

  • limits on Non-SM h production

  • limits on H++/H--

  • Summary

36×36 bunches

396 ns bunch crossing

Stephanie Beauceron - LPNHE Paris VI et VII


Tevatron current and projected performance

Tevatron: current and projected performance

FY’04 Integrated Luminosity

Measured luminosity

Integrated Luminosity (fb-1)

11/23/03 1/18/04 3/14/04

12 pb-1 / week is also above the design projection

design: challenging

base: conservative

36×36 bunches

396 ns bunch crossing

Start of Fiscal Year

Stephanie Beauceron - LPNHE Paris VI et VII


Standard model higgs

Standard Model Higgs

H bb

H  WW(*)

Dominant decay modes

  • Production cross sections are small 0.1 - 1 pb depending on MH

  • MH 135 GeV

    gg  H  bb dominated by QCD background

     searches can be performed inW/Z associatedproduction to handle backgrounds

  • MH >135 GeV

    gg  H WW(*)l+l- final states can be explored at higher masses

Production Cross section

Stephanie Beauceron - LPNHE Paris VI et VII


New ew constraint

New EW constraint

Constraint mH in the Standard Model

Old Top mass combination

New Top mass combination using new DØ run I measurement

Direct searches at LEP2: mH>114.4 GeV @95%CL

Stephanie Beauceron - LPNHE Paris VI et VII


Higgs beyond the standard model

Higgs Beyond the Standard Model

  • MSSM

    • 5 physical Higgs:

      • Two CP-even scalars: h (lighter, SM-like), H (heavier)

      • CP-odd scalar: A

      • Charged Higgs pair: H±

    • At tree-level, two free parameters

      • Ratio of vacuum expectation values:

      • One higgs mass

  • Other Possibilities

    • Left-Right Symmetric, Little Higgs, Higgs Triplet models: Doubly Charged Higgs

    • SM extensions that suppress fermion couplings

      • Fermiophobic Higgs

      • TopColor Higgs

MSSM Higgs Production Cross section

Large enhancement of rates over HSMbb

MSSM Higgs Main Decay

h/H/Abb ~ 90%

h/H/A ~ 10%

H+ ~ 100% (tan>1)


B jet tagging

b-jet tagging

DØ RunII Preliminary

  • DØ in Run II is able to b-tag up to |η| < 2.5

  • Performance being improved

  • Essential for Hbb searches

  • Can make use of the track impact parameter (IP) measurements or secondary vertex reconstruction

  • CDF:performance of sec. vtx. algorithm (after kinematics cuts)

    • ~50% b-tagefficiency for~0.6%light quarkmis-tagrate in|η| < 1

b-tagging efficiency vs light quark mis-tag rate

Both experiments are demonstrating good b-tagging capabilities

Stephanie Beauceron - LPNHE Paris VI et VII


D w e n b b production 1

DØ: W(en)bb production (1)

Motivation:

Background to WH production

Event selection

Central isolatede, pT > 20 GeV

Missing ET> 25 GeV

≥ two jets:ET > 20 GeV, |η| < 2.5

2587 evts. in Lint=174 pb-1 of data

  • Simulations with Alpgen plus Pythia through detailed detector response

  • Cross sections normalized to MCFM NLO calculations

Good understanding of data

Stephanie Beauceron - LPNHE Paris VI et VII


D w e n b b production 2

DØ: W(en)bb production (2)

Observe8, expect8.3±2.2

Bkgd. dominated by top evts.

At least two b-tags

One b-tag

Require jets to be tagged, consistent result with different b-tagging algorithms

Good agreement between data and MC in both cases

Stephanie Beauceron - LPNHE Paris VI et VII


D w e n b b production 3

DØ: W(en)bb production (3)

  • W Transverse mass of 2 Tagged events, keep event with 25 GeV<MT(W)<125 GeV

We observed 5 events, expect 6.9  1.8 events

Set limits on production of (Wbb) < 20.3 pbat 95% C.L.

Stephanie Beauceron - LPNHE Paris VI et VII


D w e n b b production 4

DØ: W(en)bb production (4)

  • Optimize Wbb signal by suppressing the top production by requiring exactly two jets

  • Observe2 evts., expect2.5±0.5

  • Sample composition

  • Requiring all jets to be b-tag by the 3 b-tagging algorithms of DØ to reduce the background

  •  Observe 2 evts., expect 0.3±0.1 (Bckd) + 0.6±0.2 Wbb (Signal)

Probability(B)=0.04 ; Probability(S+B)=0.23

Standard Model without Wbb disfavored at 2  level

Stephanie Beauceron - LPNHE Paris VI et VII


Higgs searches at tevatron st phanie beauceron lpnhe paris

3 views of high dijet mass (220 GeV) Wbb (WH) candidate

Vertex view of 2nd candidate

dijet mass (48 GeV)

ETmiss


D w e n h bb production

DØ: W(en) H(bb) production

Observe2 evts., expect2.5±0.5

In Mass windows [85-135] we observe: 0 events0.54 ± 0.14 expect background0.03 ± 0.01 WH

Systematics studies:

Set limits on production of(WH)B(Hbb) < 12.4 pb for MH = 115 GeV at 95% C.L.

Stephanie Beauceron - LPNHE Paris VI et VII


Cdf w e n mn h bb production 1

CDF: W(en/mn)H(bb) production (1)

Event selection

Central isolatede/, pT > 20 GeV

Missing ET> 20 GeV

Two jets:ET > 15 GeV, || < 2

Veto

Di-lepton, extra jet

 Observe 2072 events in data in Lint=162 pb-1

Simulations performed with Alpgen plus Herwig passed through detailed detector response

Good agreement between

data and MC

Stephanie Beauceron - LPNHE Paris VI et VII


Cdf w e n mn h bb production 2

CDF: W(en/mn)H(bb) production (2)

Enrich the b-content of events

Require at least one b-tagged jet

 Observe 62 events in data

 Expect 61 ± 5 events

Main contributions to the bkgd:

Expect0.3 evtsfrom Higgs

Signal acceptance of ~ 1.8% for

MH = 110 – 130 GeV

good agreement between

data and MC

Stephanie Beauceron - LPNHE Paris VI et VII


Cdf w e n mn h bb production 3

CDF: W(en/mn)H(bb) production (3)

Set limits on the Higgs production cross section times branching fraction at 95% C.L. :

×B < 5 pb

Systematics studies

Exceeds CDF’s Run I limit[PRL 79, 3819(1997)]

×B < 14 – 19 pb forMH = 70 – 120 GeV

Stephanie Beauceron - LPNHE Paris VI et VII


D z ee mm b production 1

Motivation

Background to ZH production

Probes PDF of the b-quark

LO diagrams for ZQ

Measure cross section ratio

(Z+b)/(Z+j)

Many uncertainties cancel

DØ: Z(ee/mm)b production (1)

  • Data correspond to integrated lumi. of 184 (ee), 152 (mm) pb-1

  • Event selection

    • Isolatede/mwithpT > 15/20 GeV, |h| < 2.5/2.0

    • Z peak for signal, side bands for bkgd. evaluations

    • JetET > 20 GeV, |h| < 2.5

    • At leastone b-tagged jet

  • Simulations performed with Pythia or Alpgen plus Pythia passed through detailed detector response

  • Cross sections normalized to data

  • Relative b- and c-quark content as given by MCFM NLO calculations

Stephanie Beauceron - LPNHE Paris VI et VII


D z ee mm b production 2

DØ: Z(ee/mm)b production (2)

Transverse energy spectrum of b-tagged jets

QCD and mistag bkgd. estimated from data

MC: Pythia Zb normalized to data

Measure cross section ratio Z+b/Z+j

0.024 ± 0.005 (stat) (syst)

Theory: ~0.02 hep-ph/0312024

Systematics studies

+ 0.005

– 0.004

Stephanie Beauceron - LPNHE Paris VI et VII


D h ww l l nn final states l e m

DØ: H  WW(*)  l+l-nn final states; l=e,m

  • Event selection

    • Isolated e/m

      • pT(e1) > 12 GeV, pT(e2) > 8 GeV

      • pT(e/m1) > 12 GeV, pT(e/m2) > 8 GeV

      • pT(m1) > 20 GeV, pT(m2) > 10 GeV

    • Missing ET greater than

      • 20 GeV(ee, em);30 GeV(mm)

    • Veto on

      • Z resonance

      • Energetic jets

  • Simulations done with Pythia passed through detailed detector response

    • Rates normalized to NLO cross section values

  • Data correspond to integrated lumi. of

    ~ 180 (ee), 160 (em)and150 (mm) pb-1

Data vs MC after

evt. preselection

Stephanie Beauceron - LPNHE Paris VI et VII


D h ww l l nn final states l e m1

DØ: H  WW(*)  l+l-nn final states; l=e, m

e+

n

W+

n

W-

e-

  • Higgs mass reconstruction not possible due to two neutrinos

  • Employ spin correlations to suppress the bkgd.

    • Df(ll) variable is particularly useful

  • Leptons from Higgs tend to be collinear

Azimuthal angle between e and m

(after event pre-selection)

Higgs of 160 GeV

Good agreement between data and MC in all

final states, and all variables examined so far

Stephanie Beauceron - LPNHE Paris VI et VII


D h ww l l nn final states l e m2

DØ: H  WW(*)  l+l-nn final states; l=e, m

DØ Run II Preliminary

Signal acceptance is ~ 0.02 – 0.2 depending on the Higgs mass/final state

  • Number of events after selections

  • Dominant bkgd. in em sample

Excluded cross section times

Branching Ratio at 95% C.L.

Higgs of 160 GeV

Stephanie Beauceron - LPNHE Paris VI et VII


D neutral higgs bosons at high tan in multi jets events

DØ: Neutral Higgs Bosons at High Tan in Multi-jets Events

(=h,H,A)

  • Event Selection:

    • Multi-jet data sample

    • At least 3 jets:ET cuts on jets are optimized separately for different Higgs mass points, and for min. # jets required in the event

    •  3 b-tagged jets

    • Look for signal in the invariant mass spectrum from the two leading b-tagged jets

  • Simulations performed with Pythia or Alpgen plus Pythia passed through detailed detector response

  • Data correspond to integrated lumi. of 131pb-1

BR( ) ~ 90%

Dijet Mass

(Higgs signal at 95% C.L. exclusion limit)

Stephanie Beauceron - LPNHE Paris VI et VII


D neutral higgs bosons at high tan in multi jets events1

DØ: Neutral Higgs Bosons at High Tan in Multi-jets Events

Signal acceptance is ~ 0.2 – 1.5% depending on the Higgs mass/final state

Stephanie Beauceron - LPNHE Paris VI et VII


D search for non sm light higgs in h

DØ: Search for Non-SM Light Higgs in H

  • Data correspond to integrated lumi. of 191 pb-1

  • Event selection

    • 2 IsolatedwithpT > 25 GeV, ||<1.05 (CC) or 1.5<||<2.4 (EC)

    • pT > 35 GeV

  • Some extensions of SM contain Higgs w/ large B(H)

    • Fermiophobic Higgs : does not couple to fermions

    • Topcolor Higgs : couple to top (only non-zero fermion coupling)

  • Dominant uncertainty in background estimation is in the measurement of  mis-ID rate (~30%)

Stephanie Beauceron - LPNHE Paris VI et VII


D search for non sm light higgs in h1

DØ: Search for Non-SM Light Higgs in H

  • No clear evidence of excess

  • Perform counting experiments on optimized sliding mass window to set limit on B(H) as function of M(H)

Stephanie Beauceron - LPNHE Paris VI et VII


Cdf search for h

CDF: Search for H++

  • H++/H-- predicted in models that contain Higgs triplets

    • Left-Right (LR) symmetric models

    • SUSY LR models : low mass (~100 GeV – 1 TeV)

  • Event selection

    • 1 pair of same sign ee, or , or ein mass window of 10%*M(H++)(~3 detector resolution)

  • same sign leptons decay contains low SM backgrounds, provide clean environment for new physics search

  • Data correspond to integrated lumi. of 240 pb-1


Cdf search for h1

CDF: Search for H++

  • Background prediction for M(l+ l+) >80 GeV (>100 GeV for ee)

  • Data : observe 0 event

Stephanie Beauceron - LPNHE Paris VI et VII


P rospectives for higgs

Prospectives for Higgs

  • New study from CDF + DØ :

  • Improvement of the results with a detailed simulation.

Statistical power onlySystematics not included

5sdiscovery

3sevidence

95% CL exclusion

Stephanie Beauceron - LPNHE Paris VI et VII


Summary

Summary

  • Hunting for Higgs at the Tevatron Run II has begun !

  • Understanding of the background processes to the Higgs production is gradually improving

  • Result summary:

    • (Wbb)< 20 pb

    • (WH) B(Hbb) < 12 pb (We)

    • (WH) B(Hbb) < 5 pb (We and W)

    • (Z+b)/ (Z+j) = 0.024 ± 0.005 (stat) (syst)

    • limits set on (H)B(HWW(*))

    • Search for Neutral Higgs in MSSM:

      • excludes A and h/H for masses 90-150 GeV/c2 at high tan β (>~100)

    • H++ Search:

      • Limits 115, 135, 135 GeV/c2 for exclusive HL decays to e, ee, 

      • Limits 110 GeV/c2 for exclusive HR decays to 

    • Search for H:

      • Limits are set for the Branching Ratio vs Mass for both Fermiophobic and TopColor models

        Already a lot of results and more are coming!

+ 0.005

– 0.004


The upgraded cdf and d detectors

The upgraded CDF and DØ detectors

  • New

    • silicon detector

    • drift chamber

    • TOF PID system

  • Upgraded

    • calorimeter, muon system

    • DAQ/trigger

    • displaced-vertex trigger

  • New (tracking in B-field)

    • silicon detector

    • fiber tracker

  • Upgraded

    • calorimeter, muon system

    • DAQ/trigger

    • (displaced-vertex trigger soon)

Stephanie Beauceron - LPNHE Paris VI et VII


Run i cdf h search

Run I CDF H+ Search

Stephanie Beauceron - LPNHE Paris VI et VII


D h search 1

DØ H++ Search (1)

  • search assume the H±± decay branching ratio to like-sign muons to be 100%.

  • Muon ID and analysis requirements

  • Make data quality requirements based on official good run lists

  • Select di-muon trigger events

  • Have muon identification requirements based on:

    • Track segments reconstructed in the muon system, isolation from signficant energy deposition in the calorimeter and an associated track from the central tracking system. The muon momentum is taken as the central track momentum

  • Muons are required to have pT > 15 GeV and |eta| < 2

Dimuon mass spectra at various steps of the event selection procedure

Stephanie Beauceron - LPNHE Paris VI et VII


D h search 2

DØ H++ Search (2)

  • Search assumes the H±± decay branching ratio to like-sign muons to be 100%.

  • Confidence level of the signal as a function of the H++ mass,for the left- and right-handed Higgs bosons

Stephanie Beauceron - LPNHE Paris VI et VII


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