Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector...

20
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

Transcript of Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector...

Page 1: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Univ. of Pennsylvania

Tae Min Hong

ATLAS Experiment

Higgs boson searches at ATLASRecent updates

1

Brookhaven Forum 2011First Glimpse of the Tera Scale

http://www.bnl.gov/bf2011

Page 2: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

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

Page 3: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

|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 TeVσ = 2% at 50 GeVPT

Air-core toroids + Gas-based chambers

|η| < 1.7 Fe/scintillator1.3 < |η| < 4.9 Cu/W-LAr

σ = 50% ⊕ 3%Ejet √E

2 Tesla field

Page 4: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Day in 201101/03 27/04 24/06 21/08 18/10

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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 JuneJuly Aug OctApril

Mar Sep

95% efficiency

3.3e33 peak L

4.9 fb-1 on tape

Newer

data

Presen

ted to

day

50 ns gap

distance

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]-1 s

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

Day in 201101/03 27/04 24/06 21/08 18/10

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Page 5: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

0 0.5 1 1.5 2 2.5

2.28

1.03

1.06

1.04

1.70

1.04

1.04

2.28

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

Page 6: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

[GeV] HM100 200 300 400 500 1000

H+X

) [pb

]

(pp

-210

-110

1

10= 7 TeVs

LHC

HIG

GS

XS W

G 2

010

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 productionggF is dominant (10× Tevatron)

g

gt H

H

q

qq

qWW

H

W,ZW,Zq

q

g

g

t

H

t

tt

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→γγH→WW(*)→ℓν+ℓνH→ZZ(*)→ℓℓ+ℓℓ

[GeV]HM100 200 300 400 500

BR

[pb]

!

-410

-310

-210

-110

1

10

LHC

HIG

GS

XS W

G 2

011

SM = 7TeVs

"l = e, ,",e =

q = udscbbb# 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 × decay3 mass regions

Table of events expected per fb-1

Does not include acceptance

ggF

× B

R [p

b] WW turn-on

Page 7: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Tae Min HongH → ZZ(*) → ℓℓ+ℓℓ

7

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<MH<300100 200 300

MHH→ZZ→4ℓ

Page 8: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

[GeV]4lm100 200 300 400 500 600

Even

ts/1

0 G

eV

012

34567

89

-1 Ldt = 1.96-2.28 fb = 7 TeVs

4l(*)ZZH

DATABackground

=150 GeV)H

Signal (m=220 GeV)

HSignal (m

2!=480 GeV) H

Signal (m

ATLAS

[GeV]Hm200 300 400 500 600

SM/

95%

CL

limit

on

1

10

210sObserved CL

sExpected CL 1 ! 2 !

ATLAS 4l(*) ZZH

-1Ldt = 1.96-2.28 fb=7 TeVs

sObserved CLsExpected CL

1 ! 2 !

sObserved CLsExpected CL

1 ! 2 !

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

8

[GeV]Hm100 200 300 400 500 600

SM/

95%

CL

Lim

it on

-110

1

10

ObservedExpected

ObservedExpected

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

LimitssCLCL S

Lim

its o

n observed expected

±1σ

±2σ

MH=150

MH=220Bkgs.

2xMH=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

Even

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

<180

≥180

[GeV]Hm200 300 400 500 600

SM/

95%

CL

limit

on

1

10

210sObserved CL

sExpected CL 1 ! 2 !

ATLAS 4l(*) ZZH

-1Ldt = 1.96-2.28 fb=7 TeVs

sObserved CLsExpected CL

1 ! 2 !

sObserved CLsExpected CL

1 ! 2 !

[GeV]Hm200 300 400 500 600

SM/

95%

CL

limit

on

1

10

210sObserved CL

sExpected CL 1 ! 2 !

ATLAS 4l(*) ZZH

-1Ldt = 1.96-2.28 fb=7 TeVs

sObserved CLsExpected CL

1 ! 2 !

sObserved CLsExpected CL

1 ! 2 !

Want |M(ℓ+ℓ−)-MZ|<15 with another ℓ′+ℓ′−

• Lepton selection : Two PT >20, All PT >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%

Page 9: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

• 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->llννSignature: two high pT opposite charged isolated leptons with high MET

38

pT µ = 50,126 GeVmµµ = 94 GeV

ETmiss = 161GeV

Saturday, September 3, 2011

μ

μ

Tae Min HongH → ZZ(*) → ℓℓ+νν

9

eilam gross, WIS, LHC2TSP, August 2011

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

38

pT µ = 50,126 GeVmµµ = 94 GeV

ETmiss = 161GeV

Saturday, September 3, 2011

Eve

nts

/ 5

Ge

V

110

210

310

410

510

610

Eve

nts

/ 5

Ge

V

110

210

310

410

510

610 -1 L dt = 1.04 fbData Total Background

TopZZ,WZ,WWZ

Other Backgrounds = 400 GeV)

HSignal (m

ATLAS = 7 TeVs ll ZZ H

[GeV]missTE

0 50 100 150 200 250 300Data

/ M

C

0.81

1.2

[GeV]missTE

0 50 100 150 200 250 300Data

/ M

C

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eV

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510

610

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eV

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610 -1 L dt = 1.04 fbData Total Background

TopZZ,WZ,WWZ

Other Backgrounds = 400 GeV)

HSignal (m

ATLAS = 7 TeVs ll ZZ H

[GeV]missTE

0 50 100 150 200 250 300Data

/ M

C

0.81

1.2

[GeV]missTE

0 50 100 150 200 250 300Data

/ M

C

0.81

1.2

ETmiss [GeV]

Even

ts /

5 G

eV

10k

100

1 Other bkgs.

DibosonZTop

MH = 400

[GeV]Hm200 250 300 350 400 450 500 550 600

SM/

95%

CL

limit

on

0

2

4

6

8

10

12

14ObservedExpected 1!

2!

ATLAS

=7TeVs, -1Ldt=1.04 fb

llZZH

[GeV]Hm200 250 300 350 400 450 500 550 600

SM/

95%

CL

limit

on

0

2

4

6

8

10

12

14ObservedExpected 1!

2!

ATLAS

=7TeVs, -1Ldt=1.04 fb

llZZH

PTlead = 126PTsublead = 50

Mℓℓ = 94ETmiss = 161

eilam gross, WIS, LHC2TSP, August 2011

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

38

pT µ = 50,126 GeVmµµ = 94 GeV

ETmiss = 161GeV

Saturday, September 3, 2011

μ

μ

100MH H→ZZ→4ℓ (Z→ℓν)2

300200

ETmiss

Page 10: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Want M(ℓ+ℓ−)=MZ with ETmiss

• Lepton selection : Leading PT >25 GeV

• Backgrounds : top, SM ZZ, WZ, WW

• Split data at MH=280 : ZZ become boosted

Err ~15%, σW, σtop biggest 3% ~50%reco.

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

10

[GeV]Hm100 200 300 400 500 600

SM/

95%

CL

Lim

it on

-110

1

10

ObservedExpected

ObservedExpected

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

LimitssCLCL S

Lim

its o

n

[GeV]Hm200 250 300 350 400 450 500 550 600

SM

/ 9

5%

CL lim

it o

n

0

2

4

6

8

10

12

14ObservedExpected 1!

2!

ATLAS

=7TeVs, -1Ldt=1.04 fb

llZZH

[GeV]Hm200 250 300 350 400 450 500 550 600

SM/

95%

CL

limit

on

0

2

4

6

8

10

12

14ObservedExpected 1!

2!

ATLAS

=7TeVs, -1Ldt=1.04 fb

llZZH8

6

10

4

MH [GeV]

2

[GeV]Hm200 250 300 350 400 450 500 550 600

SM/

95%

CL

limit

on

0

2

4

6

8

10

12

14ObservedExpected 1!

2!

ATLAS

=7TeVs, -1Ldt=1.04 fb

llZZH

[GeV]Hm200 250 300 350 400 450 500 550 600

SM/

95%

CL

limit

on

0

2

4

6

8

10

12

14ObservedExpected 1!

2!

ATLAS

=7TeVs, -1Ldt=1.04 fb

llZZH observed

expected

±1σ

±2σ

[GeV]Tm200 300 400 500 600 700

Even

ts /

50 G

eV

05

10152025303540

[GeV]Tm200 300 400 500 600 700

Even

ts /

50 G

eV

05

10152025303540

-1 L dt = 1.04 fbdata

Total BackgroundTopZZ,WZ,WWZ,W

= 380 GeV)H

Signal (m

ATLAS = 7 TeVs

ll ZZ H

MT [GeV]

Excluded Higgs masses• Use bins MT2 = (ETℓℓ + ETmiss)2 - (PTℓℓ+PTmiss)2

• Expected : 380 GeV is closest at 1.1×SM• Observed : 340 < MH < 450 GeV

Data

85

47

Expected SMExpected SMExpected SMExpected SMExpected SM

Total Z+j W+j top VV

105 19 8.5 30 47

55 6.0 3.1 15 31

Expected for MHExpected for MHExpected for MHExpected for MHExpected for MH

200 300 400 500 600

5.0 N/AN/AN/AN/A

N/A 10 10 4.5 1.8

MH

<280

≥280

Nearest jet same ϕ-hemi.Away ℓ

ETmiss

Δϕℓ,jet reject < 0.3

• Reject fake ETmiss from jet mismeas’t with

Page 11: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Tae Min HongH → WW(*) → ℓν+ℓν

11

ETmiss

μ

e

• H → WW(*) → ℓν+ℓν : partial reco = count

• Similar to ZZ(*) → ℓℓ+νν, but M(ℓℓ)≠MZ

• Sensitivity ~ 125<MH<200100

(Z4ℓ)2300200

MH (Wℓν)2 (Zℓν)2

Entr

ies / 0

.13

20

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60

80

100 Data stat) SM (sys WW WZ/ZZ/W

t t Single Top Z+jets W+jets (data driven)

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

+ 0 jetsllWWH

(ll) [rad]0 0.5 1 1.5 2 2.5 3

Data

/ M

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1.52 ππ/20 |ΔΦℓℓ| [rad]

Even

ts in

10

bins

20

40

60

WW

W+jetsZ+jets

top

MH=150

Err. ~50-100% in this region

Entri

es /

4 G

eV

-210-1101

10210310410510610710810910 Data stat) SM (sys

WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

eeWWH

[GeV]T,relmissE

0 20 40 60 80 100 120 140 160 180 200

Dat

a / M

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0.51

1.520

NJet=0 after pre-sel.

μ

eETmiss

ΔΦℓℓ

Page 12: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Want M(ℓ+ℓ−)≠MZ with ETmiss

• Leading lept. PT : e, μ=25

• Sublead. lept. PT : e=20, μ=15

• Backgrounds : Next slide

• ET,relmiss cut : ee, μμ=40, eμ=25

Tae Min HongH → WW(*) → ℓν+ℓν : pre-selection

12

• Definition of ET,relmiss

If such ℓ or jet in same ϕ-hemisph.,

Otherwise, ET,relmiss = ETmiss

ℓ or jet

Away ℓ

ETmiss

ET,relmiss reject if < 40, 25Δϕeeμμ

Data

1E+06

1E+05

4051

Expected SMExpected SMExpected SMExpected SMExpected SMExpected SM

Total SM WW top W+j Z+j VZ

1M 1.4k 7k 1M 1k

.1M 1.2k 6k .1M 100

4k 660 3k 300 30

Selection

Mℓℓ>15, Meµ>10

|Mℓℓ or eµ−MZ|>15

ET,relmiss

Even

ts /

4 G

eVE

ntr

ies /

4 G

eV

-210-1101

10210310410510610710810910 Data stat) SM (sys

WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

!!WWH

[GeV]T,relmissE

0 20 40 60 80 100 120 140 160 180 200

Data

/ M

C

0.51

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Z+jets

W+jets

WW

1-top

diboson ttbar10

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10k

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MH=150

Entr

ies / 4

GeV

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10

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310

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510 Data stat) SM (sys WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

!eWWH

[GeV]T,relmissE

0 20 40 60 80 100 120 140 160 180 200

Da

ta /

MC

0.51

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Entri

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eV-210

-1101

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510 Data stat) SM (sys WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

!eWWH

[GeV]T,relmissE

0 20 40 60 80 100 120 140 160 180 200

Dat

a / M

C

0.51

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ET,relmiss [GeV]

diboson

ttbarWW

1-top

Zj

Wj

10

100

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ntr

ies / 4

GeV

-210-1101

10210310410510610710810910 Data stat) SM (sys

WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

eeWWH

[GeV]T,relmissE

0 20 40 60 80 100 120 140 160 180 200

Da

ta /

MC

0.51

1.52

Z+jetsW+jets

WW

1-top

diboson ttbar10

1000

100k

0.1

MH=150

Entri

es /

4 G

eV

-210-1101

10210310410510610710810910 Data stat) SM (sys

WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

eeWWH

[GeV]T,relmissE

0 20 40 60 80 100 120 140 160 180 200

Dat

a / M

C

0.51

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eμ channel

μμ channel

ee channel

data

-der

ived

Page 13: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Tae Min HongH → WW(*) → ℓν+ℓν : backgrounds, final selection

13

BackgroundsMostly data-derived quantitites

• SM WW(*) : Mℓℓ data CR →SR w/MC ; Err~10%

• top : b-jet data CR →SR w/MC ; Err~10%

• W+jet : di-jet data CR →SR w/data ; Err~30%

• Others : MC predictions, small

Higgs SR SM WW CR

Even

ts /

5 G

eV

1

100

10

En

trie

s /

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eV

-210

-110

1

10

210

310

410

510 Data stat) SM (sys WW WZ/ZZ/W

t t Single Top Z+jets W+jets

H [150 GeV]

ATLAS Preliminary-1 L dt = 1.70 fb = 7 TeV, s

!eWWH

[GeV]!eM0 50 100 150 200 250

Da

ta /

MC

0.51

1.52

Entri

es /

5 G

eV

-210

-110

1

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310

410

510 Data stat) SM (sys WW WZ/ZZ/W

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Expected SMExpected SMExpected SMExpected SMExpected SMExpected SM

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Page 14: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Tae Min Hong

14

H → WW(*) → ℓν+ℓν : results

Entr

ies / 1

0 G

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Excluded Higgs masses• Expected : 135 < MH < 196 GeV

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Page 15: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

•  !"#$%&'()*"%&'+,-./#"%0-,1%-,-*$&'&2%

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Tae Min HongH → γγ

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Page 16: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

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j + jjjDYStatistical errorTotal error

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Tae Min HongH → γγ : analysis, results

16

Excluded Higgs masses• Fit with exponential + signal shape.

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Page 17: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

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Page 18: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

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Low Medium High

MH [GeV]

Page 19: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Not allowed below

Phys. Rept. 459 (2008)

~Excluded w/ gaps by ATLAS

LEP bound

It’s an exciting time to study Higgs physics!

Tae Min HongFuture outlook

19

Next steps• Analysis : Lower lep. PT; multivar. techn.

• Background : Improve data-derived est.

• Prepare for : LHC upgrades of lumi, √s

[GeV] HM100 200 300 400 500 600 700 800 900 1000

H+X

) [pb

]

(pp

-110

1

10

210

LHC

HIG

GS

XS W

G 2

010

=14 TeVs

H+X at

pp

=7 TeVs

H+X at

pp

[GeV] HM100 200 300 400 500 600 700 800 900 1000

H+X

) [pb

]

(pp

-110

1

10

210

LHC

HIG

GS

XS W

G 2

010

=14 TeVs

H+X at

pp

=7 TeVs

H+X at

pp

[GeV] HM100 200 300 400 500 600 700 800 900 1000

H+X

) [pb

]

(pp

-110

1

10

210

LHC

HIG

GS

XS W

G 2

010

=14 TeVs

H+X at

pp

=7 TeVs

H+X at

pp

√s = 14 TeV

√s = 7 TeV

3x increase at MH = 120

MH [GeV]

Still allowed!

Implications• Exp’t limits on MH help constrain the upper

bound on Λ, the scale of new physics

Not allowed above

Page 20: Higgs boson searches at ATLAS - indico.bnl.gov€¦ · Tae Min Hong 2 Outline • ATLAS detector • Selected Higgs searches ‣ H → ZZ(*) → ℓℓ+ℓℓ ‣ H → ZZ(*) →

Tae Min HongReferences & Thanks

20

Slide Source3 http://www.interactions.org/cms/?pid=2100&image_no=CE01554 https://twiki.cern.ch/twiki/bin/view/AtlasPublic/LuminosityPublicResults4 http://www.interactions.org/cms/?pid=2100&image_no=CE01525 From S. Kortnerʼs ATLAS Week Higgs talk on Oct. 11, 2011 (ATLAS internal)

6, 15 http://cdsweb.cern.ch/record/1385868/files/ATL-PHYS-SLIDE-2011-578.pdf6 https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CrossSections

7-8 https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-131/9 E. Grossʼ talk https://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=141983

9-10 http://arxiv.org/abs/1109.335711 https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-015/

11-14 https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-134/15-16 http://arxiv.org/abs/1108.5895

17 https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2011-135/18 https://twiki.cern.ch/twiki/bin/view/AtlasPublic/HiggsPlotsLPCCCombination19 A. Djouadiʼs paper http://arxiv.org/abs/hep-ph/0503172 Phys. Rept. 459 (2008)

Bill MurrayEilam Gross

Rami VanguriJohn Alison

Josh KunkleKétévi Assamagan

Thanks

References

to ATLAS & LHC for excellent operations. I’d also like to acknowledge my colleagues who helped me prepare for this talk: