Combined measurement of the Higgs boson mass in pp collisions at - - PowerPoint PPT Presentation

SLIDE 1

Combined measurement of the Higgs boson mass in pp collisions at √s=7 TeV and 8 TeV with the ATLAS and CMS experiments

Hongtao Yang

US LHC User Organization Annual Meeting Fermilab, Nov. 13, 2015

University of Wisconsin

SLIDE 2

US LUA 11/13/15 Hongtao Yang (Wisconsin)

Motivation

• Higgs boson mass (mH) is a fundamental parameter of SM

without a-priori expected value

• This measurement provides current best knowledge of mH

based on LHC Run 1 data collected by ATLAS and CMS

➡ Input for future Higgs-related measurements/studies

2

• Benefits of cooperation: valuable

experience combining Higgs measurements between ATLAS and CMS experiments at LHC

• Better understanding of the other

experiment: performance, analysis strategies, systematic uncertainties etc.

• Accumulated experience benefits
• ngoing/future combinations/analyses

A world record for the length of the author list!

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Input ATLAS analyses

• mHATLAS = 125.36 ± 0.41 GeV

= 125.36 ± 0.37 (stat.) ± 0.18 (syst.) GeV

3

[GeV]

γ γ

m 110 120 130 140 150 160

weights - fitted bkg

∑

• 8
• 6
• 4
• 2

2 4 6 8

weights / GeV

∑

20 40 60 80 100 120 140 160 180 200

Data Combined fit: Signal+background Background Signal = 7 TeV s

• 1

Ldt = 4.5 fb

∫

= 8 TeV s

• 1

Ldt = 20.3 fb

∫

s/b weighted sum Mass measurement categories

ATLAS

[GeV]

l 4

m 80 90 100 110 120 130 140 150 160 170 Events / 2.5 GeV 5 10 15 20 25 30 35

Data = 1.66) µ = 124.5 GeV

H

Signal (m Background ZZ* t Background Z+jets, t Systematic uncertainty

l 4 → ZZ* → H

• 1

Ldt = 4.5 fb

∫

= 7 TeV: s

• 1

Ldt = 20.3 fb

∫

= 8 TeV: s

ATLAS

mH=125.98 ± 0.42 (stat.) ± 0.28 (syst.) GeV

mH=124.51 ± 0.52 (stat.) ± 0.06 (syst.) GeV

H→γγ PRD 90, 052004 (2014)

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(GeV)

l 4

m

80 100 120 140 160 180

Events / 3 GeV

5 10 15 20 25 30 35

Data Z+X ,ZZ

*

γ Z =126 GeV

H

m

CMS

• 1

= 8 TeV, L = 19.7 fb s ;

• 1

= 7 TeV, L = 5.1 fb s

0.5 1 1.5 2 2.5 3 3.5 4

(7 TeV)

• 1

(8 TeV) + 5.1 fb

• 1

19.7 fb

CMS

γ γ → H

0.34 GeV ± = 124.70

H

m

0.23 − 0.26 +

1.14 = µ

3

10 ×

(GeV)

γ γ

m

110 115 120 125 130 135 140 145 150

• 100

100 200

B component subtracted

S/(S+B) weighted events / GeV

S/(S+B) weighted sum

Data S+B fits (weighted sum) B component σ 1 ± σ 2 ±

Input CMS analyses

• mH

CMS = 125.02 +0.29-0.31 GeV

= 125.02 +0.26-0.27 (stat.) +0.14-0.15 (syst) GeV

4

mH=124.70 ± 0.31 (stat.) ± 0.15 (syst.) GeV

PRD 89, 092007 (2014)

EPJ C 74 (2014) 3076

mH= 125.59 +0.43-0.41 (stat.) +0.16-0.18 (syst.) GeV

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Some details…

• Workflow:
• 1. Construct combined likelihood model from input analyses
• 2. Perform maximum likelihood fits to derive measurement results
• Correlations (especially between experiments):
• Production cross section ⨉ branching fraction

❖ Same physics: correlated between two experiments ❖ Minimal model dependency: uncorrelated between γγ and 4l. Also

uncorrelated between ggF+ttH and VBF+VH within γγ

• Systematics: very limited correlation

❖ Two independent experiments: different detectors, different

methodologies for systematic uncertainty evaluation

❖ Only correlate common theory uncertainties and part of luminosity

uncertainties: trivial impact on mass measurement

5

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[GeV]

H

m

123 124 125 126 127 128 129

Total Stat. Syst. CMS and ATLAS Run 1 LHC

Total Stat. Syst. l +4 γ γ CMS + ATLAS 0.11) GeV ± 0.21 ± 0.24 ( ± 125.09 l 4 CMS + ATLAS 0.15) GeV ± 0.37 ± 0.40 ( ± 125.15 γ γ CMS + ATLAS 0.14) GeV ± 0.25 ± 0.29 ( ± 125.07 l 4 → ZZ → H CMS 0.17) GeV ± 0.42 ± 0.45 ( ± 125.59 l 4 → ZZ → H ATLAS 0.04) GeV ± 0.52 ± 0.52 ( ± 124.51 γ γ → H CMS 0.15) GeV ± 0.31 ± 0.34 ( ± 124.70 γ γ → H ATLAS 0.27) GeV ± 0.43 ± 0.51 ( ± 126.02

Mass measurement results

ATLAS+CMS, γγ+4l mH = 125.09 ± 0.24 GeV = 125.09 ± 0.21 (stat.) ± 0.11 (syst.) GeV

6

PRL 114 (2015) 191803

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mH vs. signal yield contours

Minimal model-dependency

7

[GeV]

H

m 124 124.5 125 125.5 126 126.5 127

=125.09 GeV)

H

m (

SM

σ / σ = S 0.5 1 1.5 2 2.5 3 CMS and ATLAS Run 1 LHC

γ γ → H ATLAS l 4 → ZZ → H ATLAS γ γ → H CMS l 4 → ZZ → H CMS All combined Best fit 68% CL

PRL 114 (2015) 191803

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0.05 0.1

ATLAS

Observed Expected

combined result Uncertainty in ATLAS

0.05 0.1

[GeV]

H

m δ

CMS

Observed Expected

combined result Uncertainty in CMS

0.02 0.04 0.06

Combined

Observed Expected

combined result Uncertainty in LHC

Theory uncertainties Additional experimental systematic uncertainties Integrated luminosity background modeling γ γ → H ATLAS Muon momentum scale & resolution CMS electron energy scale & resolution calibration ee → Z vertex & conversion γ γ → H ATLAS reconstruction Photon energy resolution ECAL lateral shower shape ECAL longitudinal response Material in front of ECAL ATLAS ECAL non-linearity / photon non-linearity CMS

CMS and ATLAS Run 1 LHC

Systematic uncertainties

8

PRL 114 (2015) 191803

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0.05 0.1

ATLAS

Observed Expected

combined result Uncertainty in ATLAS

0.05 0.1

[GeV]

H

m δ

CMS

Observed Expected

combined result Uncertainty in CMS

0.02 0.04 0.06

Combined

Observed Expected

combined result Uncertainty in LHC

Theory uncertainties Additional experimental systematic uncertainties Integrated luminosity background modeling γ γ → H ATLAS Muon momentum scale & resolution CMS electron energy scale & resolution calibration ee → Z vertex & conversion γ γ → H ATLAS reconstruction Photon energy resolution ECAL lateral shower shape ECAL longitudinal response Material in front of ECAL ATLAS ECAL non-linearity / photon non-linearity CMS

CMS and ATLAS Run 1 LHC

Systematic uncertainties (cont’d)

• Syst. uncertainty dominated by E/p scale and resolution of γ, e and μ
• Theory uncertainty almost have no impact on results

✴ Interference between signal and continuum bkg. not considered though 9

PRL 114 (2015) 191803

Energy/momentum scale and resolution uncertainties on photons, electrons and muons Other experimental uncertainties

Theory uncertainties

Uncertainty contribution

0.11 GeV

0.02 GeV

0.01 GeV

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Conclusion

• ATLAS+CMS combined measurement of the Higgs

boson mass in the H→γγ and H→4l channels based on LHC Run 1 data mH = 125.09 ± 0.24 GeV = 125.09 ± 0.21 (stat.) ± 0.11 (syst.) GeV

• Total uncertainty dominated by statistical uncertainty
• Systematic uncertainty dominated by energy/

momentum scale and resolution uncertainties

• Good consistency among input analyses
• Already achieved <2‰ precision. Stay tuned for even

better results from Run 2 data!

10

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Back up

11

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ATLAS photon reconstruction

• Liquid Argon sampling calorimeter with 3 layers (+ pre-sampler for |η|<1.8):
• Provides longitudinal shower information
• Photon conversion reconstructed by matching tracks consistent with conversion
• Photon pointing used for photon vertex selection: Improves resolution at high

pile-up

12 ATLAS-CONF-2011-161 CERN/LHCC/96-041 (1996)

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CMS photon reconstruction

• High granularity PbWO4 crystal layout
• Sliding window / dynamic clustering algorithm to reconstruct

bremsstrahlung and converted photons (“superclusters” in CMS)

• Lateral shower shape distinguishes converted from unconverted

photon

• Rely on tracks (recoil) to assign photon vertex

13

E3⨉3 ESC

CERN-LHCC-2006-001

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ATLAS photon calibration

• Monte Carlo based energy calibration using

multivariate techniques

• Additional corrections from Z→ee MC/data

comparison

• Validate with real photons in data

14

[GeV]

T

E 10 20 30 40 50 60 Scale ∆

• 0.02
• 0.015
• 0.01
• 0.005

0.005 0.01 0.015 0.02 Unconverted photons Data Calibration uncertainty ATLAS

• 1

= 20.3 fb t d L

∫

= 8 TeV, s

PRD 90, 052004 (2014)

[GeV]

γ ll

m

60 70 80 90 100 110 120 Events / GeV 500 1000 1500 2000 2500 3000 Unconverted photons , data γ µ µ → Z , MC γ µ µ → Z , data γ ee → Z , MC γ ee → Z

• 1

Ldt = 20.3 fb

∫

= 8 TeV, s

ATLAS

EPJ C 74 (2014) 3071

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raw

/E

true

E

0.6 0.8 1 1.2 1.4 1.6 1.8 2

Events/0.014

• 1

10 1 10

2

10

3

10

4

10

5

10 8 TeV

CMS

Simulation

Barrel > 25 GeV

T

, p γ γ → H Photons Sum of pdfs

40 60 80 100

Relative response 0.998 1 1.002 1.004

9

Barrel high R

40 60 80 100

CMS

(8 TeV)

• 1

19.7 fb

9

Barrel low R

40 60 80 100 0.995 1 1.005

9

Endcap high R /2 (GeV)

T

• r H

T

E

40 60 80 100

9

Endcap low R

data/MC

ee

m E/p data/MC

CMS photon calibration

• Dedicated calibration of photon energy scale
• Reconstruct “e as γ” by removing tracks
• Calibration determined as function of photon ET

to account for non-linear response of calorimeter

15

• J. Instrum 10 (2015) P08010

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Electron calibration

• Electron (for H→4e/2e2μ) scale set from Z→ee

decay

• With J/ψ (+Υ) for validation at low pT

16

[GeV]

T

E 10 20 30 40 50 60 70 80 90 100 Scale ∆

• 0.02
• 0.015
• 0.01
• 0.005

0.005 0.01 0.015 0.02

• e

+

e → ψ J/

• e

+

e → Z Calibration uncertainty

|<0.60 η Electrons, | ATLAS

• 1

=20.3 fb t d L

∫

=8 TeV, s

(GeV)

T

p Electron

10 20 30 40 50 60 70

PDG

m ) /

MC peak

m

• data

peak

m (

• 0.004
• 0.003
• 0.002
• 0.001

0.001 0.002 0.003 0.004

| 0.0-0.8 η Z, | | 0.8-1.5 η Z, | | 1.5-2.5 η Z, | | 0.0-1.5 η , | Υ | 0.0-1.5 η , | Ψ J/

• 1

= 8 TeV, L = 19.7 fb s CMS

PRD 90, 052004 (2014) PRD 89, 092007 (2014) JINST 10 (2015) P06005

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ATLAS e/γ calibration procedure

17

SIMULATION! DATA!

J/ψ!ee ! Z!eeγ! data-driven ! scale validation!

calibrated ! e/γ ! energy!

Z!ee ! data-driven resolution smearing ! and scale calibration!

e/γ ! energy! 6 5

equalization of uniformity response! HV! IMW! Gain!

4

MC-based ! e/γ response ! calibration!

3

equalization of longitudinal layer response! training of MVA e/γ calibration!

EM cluster! energy!

E0! E1/E2!

1 2

EPJ C 74 (2014) 3071

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CMS R9 distribution

18

9

R

0.4 0.5 0.6 0.7 0.8 0.9 1 Fraction of events/ 0.005 0.05 0.1 0.15 0.2 0.25 γ Unconverted or late converted γ Converted > 25 GeV

T

, p γ γ → H 8 TeV

CMS

Simulation

• J. Instrum 10 (2015) P08010

R9=E3⨉3/ESC

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• f the leading muon

η

• 2
• 1

1 2

MC µ µ

/ m

Data µ µ

m 0.995 0.996 0.997 0.998 0.999 1 1.001 1.002 1.003 1.004 1.005 ATLAS

CB muons =8 TeV s Data 2012,

• 1

L dt = 20.3 fb

∫

µ µ → Z µ µ → Υ µ µ → ψ J/

(GeV)

T

p Muon

10 20 30 40 50 60 70

PDG

m ) /

MC peak

m

• data

peak

m (

• 0.004
• 0.003
• 0.002
• 0.001

0.000 0.001 0.002 0.003 0.004

CMS

• 1

= 8 TeV, L = 19.7 fb s

| 0.0-2.4 η Z, | | 0.0-0.7 η , | Υ | 1.5-2.4 η , | Υ | 0.0-0.4 η , | Ψ J/ | 0.8-1.2 η , | Ψ J/ | 1.6-2.0 η , | Ψ J/

Muon calibration

• Muon momentum scale/resolution corrected largely due to

tracker mis-alignment

• Inclusion of J/ψ (Υ) allows for calibration (validation) down to very

low momentum muons to cover full phase space of H→4μ/2μ2e

19

PRD 90, 052004 (2014) PRD 89, 092007 (2014)

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Input analyses and dataset

• What we combine: H→γγ and H→4l from ATLAS

and CMS

• Channels with best mass resolutions and

excellent sensitivity

❖ σm/m~1-2%. Other channels either have worse

resolution (O(10%)) or not sensitive

• Full reconstruction of Higgs four-vector: less

model-dependency

• LHC Run 1 dataset:
• ATLAS: 20.3 fb-1 @ 8 TeV; 4.5 fb-1 @ 7 TeV
• CMS: 19.7 fb-1 @ 8 TeV; 5.1 fb-1 @ 7 TeV

20

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ATLAS H→γγ analysis

• Dedicated for mass measurement: analysis designed

to minimize systematic uncertainty on mH

• Divide the inclusive diphoton sample into 10

categories with different S/B and resolution by

• pTt: projection of Higgs pT to the thrust axis
• Photon conversion status
• Photon |η|
• No tagged (non-ggF enriched) categories: only

minimal sensitivity for VBF coming from pTt categories

• Dedicated coupling analysis described at PRD 90,

112015 (2014)

21

thrustaxis

p

T

• p

Tt

p

Tl

p

T 1

p

T 2

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ATLAS H→γγ analysis

22

Category nsig FWHM [GeV] σeff [GeV] b in ±σeff90 s/b [%] s/ √ b √s=8 TeV Inclusive 402. 3.69 1.67 10670 3.39 3.50 Unconverted central low pTt 59.3 3.13 1.35 801 6.66 1.88 Unconverted central high pTt 7.1 2.81 1.21 26.0 24.6 1.26 Unconverted rest low pTt 96.2 3.49 1.53 2624 3.30 1.69 Unconverted rest high pTt 10.4 3.11 1.36 93.9 9.95 0.96 Unconverted transition 26.0 4.24 1.86 910 2.57 0.78 Converted central low pTt 37.2 3.47 1.52 589 5.69 1.38 Converted central high pTt 4.5 3.07 1.35 20.9 19.4 0.88 Converted rest low pTt 107.2 4.23 1.88 3834 2.52 1.56 Converted rest high pTt 11.9 3.71 1.64 144.2 7.44 0.89 Converted transition 42.1 5.31 2.41 1977 1.92 0.85 √s=7 TeV Inclusive 73.9 3.38 1.54 1752 3.80 1.59 Unconverted central low pTt 10.8 2.89 1.24 128 7.55 0.85 Unconverted central high pTt 1.2 2.59 1.11 3.7 30.0 0.58 Unconverted rest low pTt 16.5 3.09 1.35 363 4.08 0.78 Unconverted rest high pTt 1.8 2.78 1.21 13.6 11.6 0.43 Unconverted transition 4.5 3.65 1.61 125 3.21 0.36 Converted central low pTt 7.1 3.28 1.44 105 6.06 0.62 Converted central high pTt 0.8 2.87 1.25 3.5 21.6 0.40 Converted rest low pTt 21.0 3.93 1.75 695 2.72 0.72 Converted rest high pTt 2.2 3.43 1.51 24.7 7.98 0.40 Converted transition 8.1 4.81 2.23 365 2.00 0.38

PRD 90, 052004 (2014)

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CMS H→γγ analysis

• Same analysis used for mass and coupling measurements
• Untagged (ggF enriched) categories defined by Boost

decision tree (BDT) scores

• Tagged categories capture decay topologies from different

production mechanisms

23

(GeV)

γ γ

m

110 120 130 140

Events / ( 0.5 GeV )

50

Simulation Parametric model = 1.87 GeV

eff

σ FWHM = 3.10 GeV 8TeV Combined

CMS

Unpublished

EPJ C 74 (2014) 3076

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CMS H→γγ analysis

24

EPJ C 74 (2014) 3076

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ATLAS H→4l analysis

• 2D fit: m4l and BDT trained to reject ZZ

background

25

[GeV]

l 4

m

• utput

ZZ*

BDT 0.02 0.04 0.06 0.08 0.1

• 1
• 0.5

0.5 1 110 115 120 125 130 135 140

Data = 1.66) µ = 124.5 GeV

H

Signal (m Background ZZ*, Z+jets

l 4 → ZZ* → H

• 1

Ldt = 4.5 fb

∫

= 7 TeV: s

• 1

Ldt = 20.3 fb

∫

= 8 TeV: s

ATLAS [GeV]

H

m Λ

• 2ln

2 4 6 8 10 12 14 121 123 125 127 129

4e µ 4 µ 2e2 2e µ 2 Combined

σ 1 σ 2

ATLAS

l 4 → ZZ* → H

• 1

Ldt = 4.5 fb

∫

= 7 TeV: s

• 1

Ldt = 20.3 fb

∫

= 8 TeV: s

Dashed without systematics Dashed without systematics

PRD 90, 052004 (2014)

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CMS H→4l analysis

• 3D fit: m4l, kinematic discriminator for rejecting

background, and per-event mass uncertainty

26

(GeV)

l 4

m

120 130 140 150 160 170 180

bkg kin

D

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0.05 0.1 0.15 0.2 0.25

4e µ 4 µ 2e2

CMS

• 1

= 8 TeV, L = 19.7 fb s ;

• 1

= 7 TeV, L = 5.1 fb s

(GeV)

H

m

122 124 126 128 130 132

ln L

• 2

1 2 3 4 5 6 7 8 9 10

Combined

Combined (stat. only)

4e

• ZZ
• H

µ 2e2

• ZZ
• H

µ 4

• ZZ
• H
• 1

= 8 TeV, L = 19.7 fb s ;

• 1

= 7 TeV, L = 5.1 fb s CMS

PRD 89, 092007 (2014)

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Measurement parametrization

• Minimize model dependency: Profile signal

strength μ = (σexpt × BRexpt)/(σSM × BRSM) in the fit

• Independent μ for γγ and 4l: No assumption
• n relative decay fractions
• Independent μ for ggF(+ttH) and VBF(+VH)

if sensitive: Lift constraint on production mechanism

• Three free parameters in the fit

μggF+ttHγγ, μVBF+VHγγ and μ4l

27

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Measurement parametrization: impact on ATLAS results

• In ATLAS results, overall μγγ instead of μggF+ttHγγ and μVBF+VHγγ are

profiled

• Marginal impact on ATLAS standalone results as expected

28

PRD 90, 052004 (2014)

[GeV]

H

m 123 123.5 124 124.5 125 125.5 126 126.5 127 127.5 Λ

• 2ln

1 2 3 4 5 6 7

σ 1 σ 2

ATLAS

• 1

Ldt = 4.5 fb

∫

= 7 TeV s

• 1

Ldt = 20.3 fb

∫

= 8 TeV s

l +4 γ γ Combined γ γ → H l 4 → ZZ* → H without systematics

+40 MeV for γγ

+20 MeV for comb. Much smaller compared to δmHATLAS=410 MeV

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[GeV]

H

m 124 124.5 125 125.5 126 )

H

m ( Λ 2ln − 1 2 3 4 5 6 7 CMS and ATLAS Run 1 LHC

γ γ → H l 4 → ZZ → H l +4 γ γ Combined

• Stat. only uncert.

Likelihood profile for mass measurement

29

PRL 114 (2015) 191803

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ATLAS+CMS results in γγ and 4l channels

30

[GeV]

H

m 123 124 125 126 127 )

H

m ( Λ 2ln − 1 2 3 4 5 6 7

CMS and ATLAS Run 1 LHC l 4 → ZZ → H

ATLAS CMS Combined

• Stat. only uncert.

[GeV]

H

m 124 125 126 127 )

H

m ( Λ 2ln − 1 2 3 4 5 6 7

CMS and ATLAS Run 1 LHC γ γ → H

ATLAS CMS Combined

• Stat. only uncert.

[GeV]

H

m 124.5 125 125.5 126 126.5 ) µ Signal strength ( 0.5 1 1.5 2 2.5 3 CMS and ATLAS Run 1 LHC

γ γ → H l 4 → ZZ → H l +4 γ γ Combined Best fit 68% CL 95% CL

PRL 114 (2015) 191803

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[GeV]

H

M 100 150 200 250 BR [pb] × σ

• 4

10

• 3

10

• 2

10

• 1

10 1 10

LHC HIGGS XS WG 2012

= 8TeV s

µ l = e,

τ

ν ,

µ

ν ,

e

ν = ν q = udscb b b ν

±

l → WH b b

• l

+

l → ZH b ttb → ttH

• τ

+

τ → VBF H

• τ

+

τ γ γ q q ν

±

l → WW ν

• l

ν

+

l → WW q q

• l

+

l → ZZ ν ν

• l

+

l → ZZ

• l

+

l

• l

+

l → ZZ

Additional checks

• Fix all the signal yields to SM values
• mH increased to 125.16 GeV
• Difference driven by rapid increase of BR(ZZ*) with Higgs

mass

31

• Independent signal strengths

between ATLAS and CMS

• mH increased to 125.13 GeV
• Difference driven by large

excess in ATLAS H→γγ (μ=1.30)

• SM expectation @125 GeV

δmH=0.22(stat.)±0.10(syst.) GeV

• Remove fluctuations in data

(post-fit Asimov) δmH=0.19(stat.)±0.10(syst.) GeV

LHC XS WG Twiki

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[GeV]

CMS H

m −

ATLAS H

m 2 − 1.5 − 1 − 0.5 − 0.5 1 1.5 2 )

CMS H

m −

ATLAS H

m ( Λ 2ln − 1 2 3 4 5 6 7 CMS and ATLAS Run 1 LHC

γ γ → H l 4 → ZZ → H l +4 γ γ Combined

[GeV]

l 4 H

m −

γ γ H

m 2 − 1.5 − 1 − 0.5 − 0.5 1 1.5 2 )

l 4 H

m −

γ γ H

m ( Λ 2ln − 1 2 3 4 5 6 7 CMS and ATLAS Run 1 LHC

ATLAS CMS Combined

Tension in mH between decay channels / experiments

• ΔmH(γγ-ZZ*)=-0.1±0.5 GeV
• ΔmH(ATLAS-CMS)=0.4±0.5 GeV

32

Tension in ATLAS: 2.0σ Tension in CMS: 1.6σ Tension in γγ: 2.1σ Tension in 4l: 1.3σ

PRL 114 (2015) 191803

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[GeV]

CMS H

m −

ATLAS H

m 2 − 1.5 − 1 − 0.5 − 0.5 1 1.5 2 [GeV]

l 4 H

m −

γ γ H

m 2 − 1.5 − 1 − 0.5 − 0.5 1 1.5 2 CMS and ATLAS Run 1 LHC

Best fit 68% CL 95% CL

Tension in mH between decay channels / experiments

33

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Overall compatibility

• Compatibility between mH from four input measurements:
• 10% from correlating signal strengths between ATLAS and CMS
• 7% from independent signal strengths between ATLAS and CMS

34 PRL 114 (2015) 191803

[GeV]

H

m

123 124 125 126 127 128 129

Total Stat. Syst. CMS and ATLAS Run 1 LHC

Total Stat. Syst. l +4 γ γ CMS + ATLAS 0.11) GeV ± 0.21 ± 0.24 ( ± 125.09 l 4 CMS + ATLAS 0.15) GeV ± 0.37 ± 0.40 ( ± 125.15 γ γ CMS + ATLAS 0.14) GeV ± 0.25 ± 0.29 ( ± 125.07 l 4 → ZZ → H CMS 0.17) GeV ± 0.42 ± 0.45 ( ± 125.59 l 4 → ZZ → H ATLAS 0.04) GeV ± 0.52 ± 0.52 ( ± 124.51 γ γ → H CMS 0.15) GeV ± 0.31 ± 0.34 ( ± 124.70 γ γ → H ATLAS 0.27) GeV ± 0.43 ± 0.51 ( ± 126.02

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[GeV]

H

m

123 124 125 126 127 128 129

Total Stat. Syst. CMS and ATLAS Run 1 LHC

Total Stat. Syst. l +4 γ γ CMS + ATLAS 0.11) GeV ± 0.21 ± 0.24 ( ± 125.09 l 4 CMS + ATLAS 0.15) GeV ± 0.37 ± 0.40 ( ± 125.15 γ γ CMS + ATLAS 0.14) GeV ± 0.25 ± 0.29 ( ± 125.07 l 4 → ZZ → H CMS 0.17) GeV ± 0.42 ± 0.45 ( ± 125.59 l 4 → ZZ → H ATLAS 0.04) GeV ± 0.52 ± 0.52 ( ± 124.51 γ γ → H CMS 0.15) GeV ± 0.31 ± 0.34 ( ± 124.70 γ γ → H ATLAS 0.27) GeV ± 0.43 ± 0.51 ( ± 126.02 19% (22%)

40% (46%) 18% (14%) 23% (17%)

• Obs. (Exp. @125 GeV)

Weight of each analysis

• Weight of i’th measurement

w

i=1/(δmH i) 2/∑j1/(δmH j) 2

• ATLAS combined measurement weight 35% (36%); CMS 65% (64%)

35 PRL 114 (2015) 191803

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Signal strength results

• By-product of the mass measurement
• Stay tuned for dedicated coupling

measurements results!

• Consistency in μ between ATLAS and CMS

evaluated: All within 1σ

36

Central value +δμ

• δμ

μATLAS/μCMS μ

1.24 0.18 0.16 1.21+0.30-0.24

μggF+ttHγγ

1.15 0.28 0.25 1.3+0.8-0.5

μVBF+VHγγ

1.17 0.58 0.53 —

μ4l

1.40 0.30 0.25 1.3+0.5-0.4

Signal strength = num. of observed events / num. of expected events

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mH vs. μ contours

• mH vs. μ: Expected signal yield (σ⨉BR⨉eff.⨉ℒ) varying

with mH

✴

The best fit mH in contour (125.12 GeV) is not at 125.09 GeV: Overall μ profiled

37

[GeV]

H

m 124 124.5 125 125.5 126 126.5 127 ) µ Signal strength ( 0.5 1 1.5 2 2.5 3 CMS and ATLAS Run 1 LHC

γ γ → H ATLAS l 4 → ZZ → H ATLAS γ γ → H CMS l 4 → ZZ → H CMS All combined Best fit 68% CL

PRL 114 (2015) 191803

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Uncertainties in each input analysis

38

Uncertainties in GeV ATLAS H→γγ ATLAS H→4l CMS H→γγ CMS H→4l

Observed syst.

0.27 0.04 0.15 0.17

Expected syst.

0.27 0.05 0.17 0.14

Observed stat.

0.43 0.52 0.31 0.42

Expected stat.

0.45 0.66 0.32 0.57

PRL 114 (2015) 191803

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Scale uncertainties in each input analysis

39

Uncertainties in GeV ATLAS H→γγ ATLAS H→4l CMS H→γγ CMS H→4l

ATLAS ECAL non-linearity / CMS photon non-linearity

0.14 (0.16) — 0.10 (0.13) —

Material in front of ECAL

0.15 (0.13) — 0.07 (0.07) —

ECAL longitudinal response

0.12 (0.13) — 0.02 (0.01) —

ECAL lateral shower shape

0.09 (0.08) — 0.06 (0.06) —

Photon energy resolution

0.03 (0.01) — 0.01 (<0.01) —

ATLAS H→γγ vertex & conversion reconstruction

0.05 (0.05) — — —

Z→ee calibration

0.05 (0.04) 0.03 (0.02) 0.05 (0.05) —

CMS electron energy scale & resolution

— — — 0.12 (0.09)

Muon momentum scale & resolution

— 0.03 (0.04) — 0.11 (0.10)

PRL 114 (2015) 191803

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Numbers used in the uncertainty summary plot

40

Uncertainty in ATLAS Uncertainty in CMS Uncertainty in LHC combined result [GeV]: combined result [GeV]: combined result [GeV]:

• bserved (expected)
• bserved (expected)
• bserved (expected)

Scale uncertainties: ATLAS ECAL non-linearity / 0.08 (0.10) 0.08 (0.10) 0.06 (0.07) CMS photon non-linearity Material in front of ECAL 0.10 (0.08) 0.05 (0.05) 0.05 (0.05) ECAL longitudinal response 0.07 (0.08) 0.01 (0.01) 0.02 (0.03) ECAL lateral shower shape 0.07 (0.05) 0.04 (0.05) 0.04 (0.03) Photon energy resolution 0.02 (0.01) 0.01 (<0.01) 0.02 (<0.01) ATLAS H → γγ vertex & conversion 0.03 (0.03) – 0.01 (0.01) reconstruction Z → ee calibration 0.05 (0.04) 0.03 (0.03) 0.03 (0.03) CMS electron energy scale & resolution – 0.05 (0.03) 0.03 (0.02) Muon momentum scale & resolution 0.01 (0.01) 0.07 (0.03) 0.05 (0.02) Other uncertainties: ATLAS H → γγ background modeling 0.04 (0.03) – 0.01 (0.01) Integrated luminosity 0.01 (<0.01) <0.01 (<0.01) 0.01 (<0.01) Additional experimental systematic 0.02 (<0.01) 0.01 (<0.01) 0.01 (<0.01) uncertainties Theory uncertainties <0.01 (<0.01) 0.02 (<0.01) 0.01 (<0.01) Systematic uncertainty (sum in quadrature) 0.18 (0.17) 0.14 (0.13) 0.11 (0.10) Systematic uncertainty (nominal) 0.18 (0.18) 0.14 (0.13) 0.11 (0.10) Statistical uncertainty 0.37 (0.37) 0.27 (0.28) 0.21 (0.22) Total uncertainty 0.41 (0.41) 0.30 (0.31) 0.24 (0.24) Analysis weights 35% (36%) 65% (64%) –

PRL 114 (2015) 191803

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Interference effect between Higgs signal and continuum background

• Interference effect in γγ channel is estimated to be ~20-50

MeV* for SM width

• Interference effect in 4l channel is expected to be much

smaller

✴

LHC Seminar: Combined measurement of the Higgs boson mass in pp collisions at sqrt(s) = 7 and 8 TeV at the LHC. https://indico.cern.ch/event/360243/

41

20 40 60 80 100 120 100 80 60 40 20 20 pT,H GeV MH MeV Hgq OΑS

3

Hgq OΑS

3OΑS 2

Hg OΑS

3

5 10 15 20 400 300 200 100 100 200 300 HH

SM

MH MeV Constructive Interf. Destructive Interf. SM

• L. J. Dixon, Y. Li (PRL 111 (2013) 111802)

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References

• CERN/LHCC/96-041 (1996): Liquid Argon Calorimeter Technical Design Report
• CERN-LHCC-2006-001: CMS Physics: Technical Design Report Volume 1: Detector Performance and

Software

• ATLAS-CONF-2011-161: Search for the Standard Model Higgs boson in the diphoton decay channel

with 4.9 fb-1 of ATLAS data at sqrt(s)=7 TeV

• PRD 89, 092007 (2014): Measurement of the properties of a Higgs boson in the four-lepton final state
• PRD 90, 052004 (2014): Measurement of the Higgs boson mass from the H → γγ and H → ZZ∗ → 4l

channels with the ATLAS detector using 25 fb−1 of pp collision data

• EPJ C 74 (2014) 3071: Electron and photon energy calibration with the ATLAS detector using LHC Run

1 data

• EPJ C 74 (2014) 3076: Observation of the diphoton decay of the Higgs boson and measurement of its

properties

• EPJ C 75 (2015) 212: Precise determination of the mass of the Higgs boson and tests of compatibility
• f its couplings with the standard model predictions using proton collisions at 7 and 8 TeV
• PRL 114 (2015) 191803: Combined measurement of the Higgs Boson mass in pp collisions at s√=7

and 8 TeV with the ATLAS and CMS experiments

• J. Instrum 10 (2015) P08010: Performance of photon reconstruction and identification with the CMS

detector in proton-proton collisions at √s = 8 TeV

• JINST 10 (2015) P06005: Performance of electron reconstruction and selection with the CMS detector

in proton-proton collisions at √s = 8 TeV

• PRL 111 (2013) 111802: Bounding the Higgs Boson Width through Interferometry

42