The Search for Higgs Bosons

The Search for Higgs Bosons

John ConwayUniversity of California, Davis

KITPAug 2, 2011

• This talk came from my PANIC 11 talk on SM Higgs at CMS

• To this I have added more material:

• ATLAS combined SM Higgs result• Tevatron combined SM Higgs result• MSSM Higgs from CMS

Higgs@ LHC H→ZZ H→ WW H→γγ, ττ Combination

John Conway - KITP - LHC 11 LHC 2011 4

EPS/PANIC: 1.1 fb-1

Search for SM Higgs is on with the first fb-1


John Conway - KITP - LHC 11 slide topic 5

• large radius tracking, 4T field• PbWO4 crystal ECAL


John Conway - KITP - LHC 11 pileup 6

major challenge in 2011: multiple pp interactions (“pileup”)


John Conway - KITP - LHC 11 SM Higgs Production 7

[GeV] HM100 200 300 400 500 1000

H+X

) [pb

]

A(p

p m

-210

-110

1

10= 7 TeVs

LHC

HIG

GS

XS W

G 2

010

H (NNLO+NNLL QCD + NLO EW)

App

qqH (NNLO QCD + NLO EW)

App

WH (NNLO QCD + NLO EW)

App

ZH (NNLO QCD +NLO EW)

App

ttH (NLO QCD)

App 20 pb at 120 GeV


John Conway - KITP - LHC 11 SM Higgs Production 7

[GeV] HM100 200 300 400 500 1000

H+X

) [pb

]

A(p

p m

-210

-110

1

10= 7 TeVs

LHC

HIG

GS

XS W

G 2

010

H (NNLO+NNLL QCD + NLO EW)

App

qqH (NNLO QCD + NLO EW)

App

WH (NNLO QCD + NLO EW)

App

ZH (NNLO QCD +NLO EW)

App

ttH (NLO QCD)

App 20 pb at 120 GeV

vector boson fusion


John Conway - KITP - LHC 11 SM Higgs Decay 8

[GeV]HM100 120 140 160 180 200

Bran

chin

g ra

tios

-310

-210

-110

1bb

oo

cc

gg

aa aZ

WW

ZZ

LHC

HIG

GS

XS W

G 2

010



[GeV]HM100 120 140 160 180 200

Bran

chin

g ra

tios

-310

-210

-110

1bb

oo

cc

gg

aa aZ

WW

ZZ

LHC

HIG

GS

XS W

G 2

010

WWWW: dominates over wide mass range, clean final state (lνlν)



[GeV]HM100 120 140 160 180 200

Bran

chin

g ra

tios

-310

-210

-110

1bb

oo

cc

gg

aa aZ

WW

ZZ

LHC

HIG

GS

XS W

G 2

010


ZZ

ZZ: three channels, sharp resolution



[GeV]HM100 120 140 160 180 200

Bran

chin

g ra

tios

-310

-210

-110

1bb

oo

cc

gg

aa aZ

WW

ZZ

LHC

HIG

GS

XS W

G 2

010


ZZ


ττ

ττ: four channels, can use VBF production



[GeV]HM100 120 140 160 180 200

Bran

chin

g ra

tios

-310

-210

-110

1bb

oo

cc

gg

aa aZ

WW

ZZ

LHC

HIG

GS

XS W

G 2

010

γγ

γγ: small BR, sharp resolution


ZZ


ττ




[GeV]HM100 120 140 160 180 200

Bran

chin

g ra

tios

-310

-210

-110

1bb

oo

cc

gg

aa aZ

WW

ZZ

LHC

HIG

GS

XS W

G 2

010

γγ

γγ: small BR, sharp resolution


ZZ


ττ


bb mode will play rolein future: boosted Higgs


John Conway - KITP - LHC 11 H → ZZ channels 9

Three useful H→ZZ final states:

Z → llZ → ll

Z → llZ →νν

Z → llZ → qq


John Conway - KITP - LHC 11 H → ZZ → 4 l 10

H → ZZ → 4 l• look for best reconstructed Z → ee, μμ (Mll > 60 GeV)• find second lepton pair• baseline selection: MZ2 > 20 GeV• high-mass selection: MZ2 > 60 GeV

• main background: continuum ZZ (estimate from data)

eeee μμμμ eeμμZZ 2.76±0.18 4.10±0.27 6.72±0.45

Z+jets 0.37±0.07 0.06±0.01 0.39±0.07

Z+bb,cc, tt 0.01±0.02 0.01±0.01 0.02±0.02

H (200 GeV) 0.82±0.01 1.16±0.01 1.91±0.02

observed 3 6 6

baseline



H → ZZ → 4 l

eeee μμμμ eeμμZZ 2.50±0.17 3.55±0.23 6.10±0.40

Z+jets 0.14±0.06 0.004±0.004 0.15±0.06

H (200 GeV) 0.76±0.01 1.08±0.01 1.80±0.02

observed 0 2 6

high-mass

For high-mass selection, see good agreement with ZZ background prediction.

Signal: sharp peak

]2 [GeV/c4lM100 200 300 400 500 600

2Ev

ents

/10

GeV

/c

-210

-110

1

DATA

Z+jets

ZZ2=250 GeV/cHm2=200 GeV/cHm2=150 GeV/cHm

CMS Preliminary 2011 -1 = 7 TeV L = 1.13 fbs



H → ZZ → 4 l

]2 [GeV/cHM200 300 400 500 600

SMσ/

σ95

% C

L lim

it on

0

5

10

15

20

25 Observed LimitSCL Expected LimitSCL

σ 1± Expected SCLσ 2± Expected SCL

SMσ / σ

CMS preliminary 2011 = 7 TeVs at -11.13 fb


John Conway - KITP - LHC 11 H → ZZ → 2l 2ν 13

H → ZZ → 2 l 2ν

• two opposite-sign leptons, |Mll-MZ| < 15 GeV• MET > 69-170 GeV (slides up with MH)

ee μμ



H → ZZ → 2 l 2ν

• two opposite-sign leptons, |Mll-MZ| < 15 GeV• MET > 69-170 GeV (slides up with MH)• MT window cut (slides up with MH)

ee μμ



H → ZZ → 2 l 2ν


John Conway - KITP - LHC 11 H → ZZ → 2l 2j 16

H → ZZ → 2 l 2j

[GeV]ZZm200 300 400 500 600 700

Eve

nts

/ 20

GeV

0

20

40

60

80

100

120

140-1CMS Preliminary 2011, 1.0 fb = 7 TeVs

Sideband Extrapolated Fit

0 b-tag 2l2q data

Z + Jets

tt/tW

ZZ/WZ/WW

3×400 GeV SM Higgs

[GeV]ZZm200 300 400 500 600 700

Eve

nts

/ 20

GeV

0

5

10

15

20

25-1CMS Preliminary 2011, 1.0 fb = 7 TeVs


2 b-tag 2l2q data

Z + Jets

tt/tW

ZZ/WZ/WW

3×400 GeV SM Higgs

[GeV]ZZm200 300 400 500 600 700

Eve

nts

/ 20

GeV

0

20

40

60

80

100

120

140

160

-1CMS Preliminary 2011, 1.0 fb = 7 TeVs


1 b-tag 2l2q data

Z + Jets

tt/tW

ZZ/WZ/WW

3×400 GeV SM Higgs

0 b tag 1 b tag 2 b tag

• two opposite-sign leptons 70 < Mll < 110 GeV• two jets 75 < Mjj < 105 GeV• MZZ ∈ [183,800] GeV


John Conway - KITP - LHC 11 H → ZZ → 2l 2j 17

H → ZZ → 2 l 2j

[GeV]HM250 300 350 400 450 500 550 600

SMσ

/ 95

%σ

024

68

101214

161820

ObservedSCL ExpectedSCL


SM



John Conway - KITP - LHC 11 H → WW → 2l 2ν 18

• in H → WW decays the W spins are anti-aligned:

• in the decays of both W’s to lν, the leptons tend to come out in the same direction

H WW⇒ ⇐

νν

l

l



• in H → WW decays the W spins are anti-aligned:

• in the decays of both W’s to lν, the leptons tend to come out in the same direction

• use this and other kinematic variables in BDT

H WW⇒ ⇐

νν

l

l



WW + 0 jets category

]$ [ll

q6

0 50 100 150

$en

tries

/ 7

0

20

40

60

80CMS preliminary data

=130H m

WW

Z+jets

top

WZ/ZZ

W+jets

-1L = 1.1 fb

]2 [GeV/cllm

0 50 100 150 200

2en

tries

/ 5

GeV

/c

0

20

40


=130H m

WW

Z+jets

top

WZ/ZZ

W+jets

-1L = 1.1 fb



WW + 1 jets category

]$ [ll

q6

0 50 100 150

$en

tries

/ 14

0

20

40

60 CMS preliminary data=130H m

WW

Z+jets

top

WZ/ZZ

W+jets

-1L = 1.1 fb

]2 [GeV/cllm

0 50 100 150 200

2en

tries

/ 10

GeV

/c

0

20

40


=130H m

WW

Z+jets

top

WZ/ZZ

W+jets

-1L = 1.1 fb


John Conway - KITP - LHC 11

MVA Output-1 -0.5 0 0.5 1

entri

es

0

20

40

CMS preliminary data=150H m

WW

Z+jets

top

WZ/ZZ W+jets

-1L = 1.1 fb

MVA Output-1 -0.5 0 0.5 1

entri

es

0

20

40

CMS preliminary data=150H m

WW

Z+jets

top

WZ/ZZ W+jets

-1L = 1.1 fb

H → WW → 2l 2ν 22

also split into same-flavor and opposite-flavor:

opposite flavor(WW+0 jets)

same flavor(WW+0 jets)

also include WW + 2 jets channel...



)2Higgs boson mass (GeV/c120 140 160 180 200 220 240

SMσ/

95%

σ lim

it S

CL

1

10

ExpectedSCLσ 1± Expected SCLσ 2± Expected SCL

ObservedSCL

-1 = 1.1 fbint WW combined, L→H = 7 TeVsCMS Preliminary,

)2Higgs boson mass (GeV/c120 140 160 180 200 220 240

SMσ/

95%

σ lim

it S

CL

1

10


ObservedSCL

-1 = 1.1 fbint

WW combined (cuts), L→H = 7 TeVsCMS Preliminary,

cut based BDT based

Exclude SM Higgs in range 150 < MH < 193 GeV

“Interesting” excess in low mass range!


John Conway - KITP - LHC 11 H → γγ 24

H → γγ

• e.m. calorimeter designed with this mode in mind!• γγ resolution: 2.4 GeV

event selection• two photons with at least 40, 30 GeV pT

• choose vertex based on PV tracks or conversions

• 8 classes: barrel/endcap ⊗ pTγγ > 40 GeV ⊗ iso (R9)

(H) (GeV/c)T

p0 50 100 150 200

Frac

tion

of v

ertic

es0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

=5.6〉PUn〈SimulationCMS preliminary

| < 10 mmsim-zreco|z



)2 (GeV/cγ γm80 90 100 110 120 130 140 150 160 170 180

)2Ev

ents

/ (2

GeV

/c

0

100

200

300

400

500Data

γ2 prompt

γ 1 fake γ1 prompt γ2 fake

Drell-Yan

-1 = 7 TeV L = 1.09 fbsCMS preliminary

)2 (GeV/cγγm100 110 120 130 140 150

)2Ev

ents

/ ( 1

GeV

/c0

50

100

150

200

250DataBkg Modelσ1 ±σ2 ±


All Categories Combined

zoomed in, compared with background fit

mass spectrum showing background sources

signalshape



110 115 120 125 130 135

SM)aa

A(H

m/95

%CL

)aa

A(H

m

2

4

6

8

10

12

14

SMm

Observed CLs LimitObserved Bayesian LimitMedian Expected CLs Limit

Expected CLsm 1( Expected CLsm 2(


140mH (GeV/c2)

expected limit at ~4x SM


John Conway - KITP - LHC 11 H → ττ 27

Main focus of H → ττ: MSSM Higgs at large tanβ

Can exploit VBF production of SM Higgs by requiring two forward “tagging” jets in addition to tau decay channels (eτ, μτ, eμ, μμ)

e- νν 17.8%μ- νν 17.4%h-ν 49%

π- ν 11% K- ν 0.7% ρ- ν 25.4%h+h-h-ν 15%

Tau ID classes: π±/K±

π± π0

π± π0 π0 ...

π+ π- π±

(GeV/c)T

pτgenerated visible 0 20 40 60 80 100 120 140

effi

cien

cyτ

expe

cted

00.10.20.30.40.50.60.70.80.9

1

HPS looseHPS mediumHPS tight

=7 TeVsCMS Simulation 2010,


John Conway - KITP - LHC 11 MSSM H/A/h➝ττ 28

[GeV]vism0 100 200 300 400

Even

ts /

20 G

eV

-110

1

10

210

310

410CMS Preliminary

=7 TeVs -11.1 fb-channelµτµτ

Observedττ→φµµ→Zττ→Z

tt

=20)β=120, tanA

(m

[GeV]vism0 100 200 300 400 500

Even

ts

1

10

210

310CMS Preliminary

=7 TeVs -11.1 fbµτeτ

ττ→φObserved

ττ→ZttElectroweakFakes

=20)β=120, tanA

(m

[GeV]vism0 100 200 300 400 500

Even

ts

10

210

310

410CMS Preliminary

=7 TeVs -11.1 fbhτeτ

ττ→φObserved

ττ→ZttElectroweakQCD

=20)β=120, tanA

(m

[GeV]vism0 100 200 300 400 500

Even

ts

10

210

310

410CMS Preliminary

=7 TeVs -11.1 fbhτµτ

ττ→φObserved

ττ→ZttElectroweakQCD

=20)β=120, tanA

(m

eτ μτ

eμ μμ


John Conway - KITP - LHC 11 slide topic 29

[GeV]Am100 150 200 250 300 350 400 450 500

βta

n

0

10

20

30

40

50

60

CMS observed theoryσ1±

CMS expected-1D0 7.3 fb

LEPCMS 2010 observedCMS 2010 expected

95% CL excluded regions

-1CMS Preliminary 2011 1.1 fb

= 1 TeVSUSY

scenario, MmaxhMSSM m



[GeV]vism0 100 200 300 400

Even

ts /

20 G

eV-110

1

10

210 CMS Preliminary=7 TeVs -11.1 fb

-channelµτµτ

Observed,ττ→(10x)H

µµ→Zττ→Z

tt

=120Hm

eτ μτ

eμ μμ

Here we require two forward jets, tagging the vector boson fusion process



[GeV]Hm110 120 130 140

SMσ/

95%

CLs

)ττ→

x B

R(H

σ

5

10

15

20

25

30

-1 = 7 TeV, 1.1 fbsCMS preliminary Expected CLs Limit

Observed CLs Limit

expected limit at ~9x SM


John Conway - KITP - LHC 11 Combining channels 32

[GeV]Hm110 120 130 140

SMσ/

95%

CLs

)ττ→

x B

R(H

σ

5

10

15

20

25

30

-1 = 7 TeV, 1.1 fbsCMS preliminary Expected CLs Limit

Observed CLs Limit

110 115 120 125 130 135

SM)aa

A(H

m/95

%CL

)aa

A(H

m

2

4

6

8

10

12

14

SMm

Observed CLs LimitObserved Bayesian LimitMedian Expected CLs Limit

Expected CLsm 1( Expected CLsm 2(


140mH (GeV/c2))2Higgs boson mass (GeV/c

120 140 160 180 200 220 240

SMσ/

95%

σ lim

it S

CL

1

10


ObservedSCL

-1 = 1.1 fbint WW combined, L→H = 7 TeVsCMS Preliminary,

[GeV]HM250 300 350 400 450 500 550 600

SMσ

/ 95

%σ

024

68

101214

161820

ObservedSCL ExpectedSCL


SM


]2 [GeV/cHM200 300 400 500 600

SMσ/

σ95

% C

L lim

it on

0

5

10

15

20

25 Observed LimitSCL Expected LimitSCL


SMσ / σ


Goal: combine results of all six search channels

H→ZZ→4l H→ZZ→2l2ν H→ZZ→2l2j

H→WW→2l2ν H→γγ H→ττ



• form joint likelihood from all channels• include correlated and uncorrelated systematic

uncertainties represented by nuisance parameters• use CLs method to quote final limits• (agrees very well with Bayesian)



These are the first CMS results to exclude a SM Higgs boson!

)2Higgs boson mass (GeV/c100 200 300 400 500 600

SMm/

95%

mLi

mit

1

10

ObservedSCLm 1( Expected SCLm 2( Expected SCL

Bayesian Observed


Bayesian Observed

-1 = 1.1 fbintCombined, L = 7 TeVsCMS Preliminary, ObservedSCL

m 1( Expected SCLm 2( Expected SCL

Bayesian Observed

-1 = 1.1 fbintCombined, L = 7 TeVsCMS Preliminary,





SMm/

95%

mLi

mit

1

10


Bayesian Observed


Bayesian Observed



Bayesian Observed


95% CL Excluded





SMσ/

95%

σ li

mit

SC

L

1

10

210 = 7 TeVsCMS Preliminary, Combined)-1 WW (1.1 fb→H )-1 (1.1 fbγγ →H )-1 (1.1 fbττ →H )-1 4l (1.1 fb→ ZZ →H )-1 2l 2q (1.0 fb→ ZZ →H )-1 (1.1 fbν 2l 2→ ZZ →H

Combined)-1 WW (1.1 fb→H )-1 (1.1 fbγγ →H )-1 (1.1 fbττ →H )-1 4l (1.1 fb→ ZZ →H )-1 2l 2q (1.0 fb→ ZZ →H )-1 (1.1 fbν 2l 2→ ZZ →H

Combined)-1 WW (1.1 fb→H )-1 (1.1 fbγγ →H )-1 (1.1 fbττ →H )-1 4l (1.1 fb→ ZZ →H )-1 2l 2q (1.0 fb→ ZZ →H )-1 (1.1 fbν 2l 2→ ZZ →H


John Conway - KITP - LHC 11 ATLAS - channels 36

ATLAS - various channel results:


John Conway - KITP - LHC 11 ATLAS/CMS combinations 37


John Conway - KITP - LHC 11 CMS vs ATLAS 38


SMm/

95%

mLi

mit

1

10


Bayesian Observed


Bayesian Observed



Bayesian Observed


• both experiments exclude 300-450 GeV • CMS excludes 150-200 GeV, other• CMS: better sensitivity (125-425 GeV)• both experiments have low mass excess• ATLAS+CMS combination coming (LP?)


John Conway - KITP - LHC 11 ATLAS γγ 39

ATLAS low mass wiggles coming from γγ


John Conway - KITP - LHC 11 Tevatron combined result 40

Tantalizingly close to SM sensitivity! Exclude 2x SM @ 130 GeV: LHC excess


John Conway - KITP - LHC 11 SM Higgs Exclusion 41

115 120 125 130

Tevatron12 fb-1?

bbLEP LHC

2 fb-1 ?γγ, ττ

uppe

r lim

it/SM

1

2

Tevatron is not out of the game yet - the nextfew months should be interesting! Very schematically:


John Conway - KITP - LHC 11 SM Higgs Exclusion 41

115 120 125 130

Tevatron12 fb-1?

bbLEP LHC

2 fb-1 ?γγ, ττ

uppe

r lim

it/SM

1

2

Tevatron is not out of the game yet - the nextfew months should be interesting! Very schematically:

Combining LHC and Tevatron possible...can it happen?

The Search for Higgs Bosons

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