Higgs boson searches at ATLAS - · PDF file Tae Min Hong 2 Outline • ATLAS detector...

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  • Univ. of Pennsylvania

    Tae Min Hong

    ATLAS Experiment

    Higgs boson searches at ATLAS Recent updates

    1

    Brookhaven Forum 2011 First Glimpse of the Tera Scale

    http://www.bnl.gov/bf2011

    http://www.bnl.gov/bf2011 http://www.bnl.gov/bf2011

  • Tae Min Hong

    2

    Outline

    • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) → ℓℓ+νν ‣ H → WW(*) → ℓν+ℓν ‣ H → γγ

    • MH exclusion limits • Future outlook • References, Thanks

    “Higgs” is a BIG topic. I’ll focus on H → WW → ℓν+ℓν, which I work on, and 3 other SM decay modes with the best sensitivity (currently) for some mass ranges. Many decay modes that are not discussed here are also important for understanding the Higgs sector!

    MH [GeV]

    H→ZZ→4ℓ (Z→ℓν)2

    300200

    γγ

    100

    This is just a cartoon. In reality, the ranges overlap everywhere & all modes contribute.

    (W→ℓν)2

  • |η| < 3.2 Pb-LAr accordion

    Tae Min HongATLAS detector

    3

    |η| < 2.5

    σ = 10%√E ⊕ 0.7% E

    σ = 0.05% PT (GeV) ⊕ 1% PT

    |η| < 2.7

    = 10% at 1 TeV σ = 2% at 50 GeV PT

    Air-core toroids + Gas-based chambers

    |η| < 1.7 Fe/scintillator 1.3 < |η| < 4.9 Cu/W-LAr

    σ = 50% ⊕ 3% Ejet √E

    2 Tesla field

  • Day in 2011 01/03 27/04 24/06 21/08 18/10

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    40 = 7 TeVs ATLAS Online LHC Delivered

    May June July Aug OctApril

    Mar Sep Day in 2011

    01/03 27/04 24/06 21/08 18/10

    ]-1 To

    ta l I

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    7 = 7 TeVs ATLAS Online Luminosity

    LHC Delivered

    ATLAS Recorded

    -1Total Delivered: 5.21 fb -1Total Recorded: 4.88 fb

    Day in 2011 01/03 01/0403/05 03/06 05/0705/08 06/0907/10 08/11

    ]-1 s-2 cm33

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    4 4.5 = 7 TeVs ATLAS Online Luminosity

    LHC Stable Beams -1 s-2 cm33 10!Peak Lumi: 3.59

    ~100 pb-1 / day since Sept. Pile-up 50 ns bunch trains

    half a fb field17 mi around

    Tae Min HongATLAS data taking in 2011 at 7 TeV

    4

    May June July Aug OctApril

    Mar Sep

    95% efficiency

    3.3e33 peak L

    4.9 fb-1 on tape

    Ne we

    r d ata

    Pre sen

    ted to

    da y

    50 ns ga p

    distance

    Day in 2011 01/03 01/0403/05 03/06 05/0705/08 06/0907/10 08/11

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    4 4.5 = 7 TeVs ATLAS Online Luminosity

    LHC Stable Beams -1 s-2 cm33 10!Peak Lumi: 3.59

    Day in 2011 01/03 01/0403/05 03/06 05/0705/08 06/0907/10 08/11

    ]-1 s

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    4 4.5 = 7 TeVs ATLAS Online Luminosity

    LHC Stable Beams -1 s-2 cm33 10!Peak Lumi: 3.59

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    ~6

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    1.06

    1.04

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    1.04

    1.04

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    1.04

    1.06

    1.08

    fb-1

    Tae Min HongATLAS Higgs recent results

    5

    Decay Reference

    H → γγ arXiv:1108.5895

    H → ττ ATLAS-CONF-2011-133

    H → bb ATLAS-CONF-2011-103

    H → ZZ(*) → ℓℓ+ℓℓ arXiv:1109.5945

    H → ZZ(*) → ℓℓ+qq arXiv:1108.5064

    H → ZZ(*) → ℓℓ+νν arXiv:1109.3357

    H → WW(*) → ℓν+ℓν ATLAS-CONF-2011-134

    H → WW(*) → ℓν+qq arXiv:1109.3615

    MSSM H → ττ ATLAS-CONF-2011-132

    MSSM H+ ATLAS-CONF-2011-138

    SM Higgs combination ATLAS-CONF-2011-135

    We have ~5 fb-1 on tape; see p.20.

    1.03

    1.96

  • [GeV] HM 100 200 300 400 500 1000

    H +X

    ) [ pb

    ]

    (p p

    -210

    -110

    1

    10 = 7 TeVs

    LH C

    H IG

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    G 2

    01 0

    H (NNLO+NNLL QCD + NLO EW)

    pp

    qqH (NNLO QCD + NLO EW)

    pp

    WH (NNLO QCD + NLO EW)

    pp ZH (NNLO QCD +NLO EW)

    pp

    ttH (NLO QCD)

    pp

    Tae Min Hong

    6

    Higgs production, decay

    Higgs production ggF is dominant (10× Tevatron)

    g

    g t H

    H

    q

    q q

    q W W

    H

    W,Z W,Zq

    q

    g

    g

    t

    H

    t

    t t

    Gluon-gluon fusion (ggF) Vector-boson fusion (VBF)

    Associated prod’n

    MH=120 MH=150 MH=300

    43 16 0.04

    127 390 89

    1.5 4.6 3.8

    Decay

    H→γγ H→WW(*)→ℓν+ℓν H→ZZ(*)→ℓℓ+ℓℓ

    [GeV]HM 100 200 300 400 500

    B R

    [p b]

    !

    -410

    -310

    -210

    -110

    1

    10

    LH C

    H IG

    G S

    XS W

    G 2

    01 1

    SM = 7TeVs

    "l = e, ,",e =

    q = udscb bb# lWH

    bb-l+ lZH

    -+ VBF H

    -+ H

    qq# lWW

    -l+ lWW

    qq-l+ lZZ -l+ lZZ

    -l+l-l+ lZZ

    ZZ turn-on

    MH [GeV] MH [GeV]

    SM Higgs at 7 TeV • ℓ = e or µ • ν = all 3 flavors • q = exclude top

    Low Medium High

    Prod’n × decay 3 mass regions

    Table of events expected per fb-1 Does not include acceptance

    gg F

    × B

    R [p

    b] WW turn-on

  • Tae Min HongH → ZZ(*) → ℓℓ+ℓℓ

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    μ

    μ

    e

    e

    85.5 GeV

    85.9 GeV

    μ

    μ

    e

    e

    M4ℓ = 209.7

    • H → ZZ(*) → ℓℓ+ℓℓ : full reco = mass peak • Clean! M(ℓ+ℓ−) ~ MZ • Sensitivity ~ 200

  • [GeV]4lm 100 200 300 400 500 600

    Ev en

    ts /1

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    eV

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    8 9

    -1 Ldt = 1.96-2.28 fb = 7 TeVs

    4l(*)ZZH

    DATA Background

    =150 GeV) H

    Signal (m =220 GeV)

    H Signal (m

    2!=480 GeV) H

    Signal (m

    ATLAS

    [GeV]Hm 200 300 400 500 600

    SM /

    95 %

    C L

    lim it

    on

    1

    10

    210 sObserved CL

    sExpected CL 1 ! 2 !

    ATLAS 4l(*) ZZH

    -1Ldt = 1.96-2.28 fb =7 TeVs

    sObserved CL sExpected CL

    1 ! 2 !

    sObserved CL sExpected CL

    1 ! 2 !

    Tae Min HongH → ZZ(*) → ℓℓ+ℓℓ : analysis

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    [GeV]Hm 100 200 300 400 500 600

    SM /

    95 %

    C L

    Li m

    it on

    -110

    1

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    Observed Expected

    Observed Expected

    1! 2!ATLAS

    =7 TeVs

    -1 L dt ~ 1.0-2.3 fb (LP 2011)

    ATLAS 2010 -1 L dt ~ 35 pb

    (2010 Data)

    2011 Preliminary

    LimitssCL

    LimitssCLC L S

    L im

    its o

    n observed expected

    ±1σ

    ±2σ

    MH=150

    MH=220 Bkgs.

    2x MH=480

    Excluded Higgs masses • 95% confidence level limits using CLS • Expected : 194 GeV is closest at 1.01×SM • Observed : 191-197, 199-200, 214-224

    Ev en

    ts /

    10 G

    eV

    1

    Data

    3

    24

    Expected SMExpected SMExpected SM

    Total SM ZZ Zbb, ttbar

    3.0 2.4 0.6

    21 21 0.3

    Expected for MHExpected for MHExpected for MHExpected for MHExpected for MH

    130 150 200 300 400

    1.0 2.3 N/AN/AN/A

    N/AN/A 5.9 3.5 2.6

    MH

    7 • Split data at MH=180 where ZZ turns-on

    • Backgrounds ‣ SM ZZ(*)→ℓℓ+ℓℓ : Use MC ; Err~15% ‣ Z+bb, b→ℓ fake : Use data ; Err~20-40% ‣ ttbar→(Wb)2, W→ℓν : Use MC ; Err~10%

  • • H → ZZ(*) → ℓℓ+νν : partial reco = count • M(ℓ+ℓ−)~MZ with ETmiss for νν • Sensitivity ~ MH>300

    eilam gross, WIS, LHC2TSP, August 2011

    Heavier Higgs: H->llνν Signature: two high pT opposite charged isolated leptons with high MET

    38

    pT µ = 50,126 GeV mµµ = 94 GeV

    ET miss = 161GeV

    Saturday, September 3, 2011

    μ

    μ

    Tae Min HongH → ZZ(*) → ℓℓ+νν

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    eilam gross, WIS, LHC2TSP, August 2011

    Heavier Higgs: H->llνν Signature: two high pT opposite charged isolated leptons with high MET

    38

    pT µ = 50,126 GeV mµµ = 94 GeV

    ET miss = 161GeV

    Saturday, September 3, 2011

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