In Situ Measurements of Jet Energy Scale in ATLAS Doug Schouten, - - PowerPoint PPT Presentation

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In Situ Measurements of Jet Energy Scale in ATLAS Doug Schouten, - - PowerPoint PPT Presentation

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In Situ Measurements of Jet Energy Scale in ATLAS Doug Schouten, Andres Tanasiczjuk, and Mike Vetterli for the ATLAS Collaboration Simon Fraser University and TRIUMF Physics in Collisions 2011 - Vancouver Introductary Remarks Jet Energy Scale

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SLIDE 1

In Situ Measurements of Jet Energy Scale in ATLAS

Doug Schouten, Andres Tanasiczjuk, and Mike Vetterli for the ATLAS Collaboration

Simon Fraser University and TRIUMF

Physics in Collisions 2011 - Vancouver

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SLIDE 2

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Introduction

◮ the jet energy scale strongly dependent

  • n details of ATLAS calorimetry, but

these will not be discussed here

◮ see 2008 JINST 3 S08003 for details

  • f the ATLAS detector, if interested
slide-3
SLIDE 3

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Introduction

◮ the jet energy scale strongly dependent

  • n details of ATLAS calorimetry, but

these will not be discussed here

◮ see 2008 JINST 3 S08003 for details

  • f the ATLAS detector, if interested

◮ this presentation: jet energy scale derived from 7 TeV collision data,

also using input from 2004 combined testbeam (CTB) and 900 GeV data

◮ focus for the scale is on robustness ◮ resolution improvements with offline compensation techniques have recently

arrived in ATLAS

◮ overall uncertainty will continue to shrink as γ + jet, multi-jet and track-jet in

situ techniques mature, and as data accumulates

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SLIDE 4

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

EM+JES Scheme

The EM scale correctly measures the energy of EM

  • showers. This is validated in Z → e+e− events for the

EM LAr, and using MIP µ’s for the Tile.

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SLIDE 5

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

EM+JES Scheme

The EM scale correctly measures the energy of EM

  • showers. This is validated in Z → e+e− events for the

EM LAr, and using MIP µ’s for the Tile. A pileup correction is applied to make the final energy correction independent of instantaneous luminosity. Correction is derived from a tower-based estimate of the pileup background.

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SLIDE 6

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

EM+JES Scheme

The EM scale correctly measures the energy of EM

  • showers. This is validated in Z → e+e− events for the

EM LAr, and using MIP µ’s for the Tile. A pileup correction is applied to make the final energy correction independent of instantaneous luminosity. Correction is derived from a tower-based estimate of the pileup background. The vertex correction corrects the momentum of the constituent clusters to point from the primary vertex with highest p2

T

  • . The jet is corrected using

vectorial addition of the corrected inputs.

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SLIDE 7

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

EM+JES Scheme

The EM scale correctly measures the energy of EM

  • showers. This is validated in Z → e+e− events for the

EM LAr, and using MIP µ’s for the Tile. A pileup correction is applied to make the final energy correction independent of instantaneous luminosity. Correction is derived from a tower-based estimate of the pileup background. The vertex correction corrects the momentum of the constituent clusters to point from the primary vertex with highest p2

T

  • . The jet is corrected using

vectorial addition of the corrected inputs. Finally, a Monte Carlo based energy correction, C(E, η), is applied that corrects to the particle level, within ±2%a

aSee extra slides for more details on the procedure for extracting these

corrections from the Monte Carlo.

[GeV]

jet T

p 20 30

2

10

2

10 × 2

3

10

3

10 × 2 Average JES correction 1 1.2 1.4 1.6 1.8 2

| < 0.8 η 0.3 < | | < 2.8 η 2.1 < | | < 4.4 η 3.6 < | = 0.6, EM+JES R

t

Anti-k

ATLAS Preliminary |

det

η Jet | 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Jet response at EM scale 0.4 0.5 0.6 0.7 0.8 0.9 1

E = 30 GeV E = 60 GeV E = 110 GeV E = 400 GeV E = 2000 GeV FCal HEC-FCal Transition HEC Barrel-Endcap Transition Barrel = 0.6, EM+JES R

t

Anti-k

ATLAS Preliminary

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SLIDE 8

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Evaluating the EM+JES

◮ overall strategy: evaluate the JES by roughly factorizing the components of EM+JES, and

verifying that the Monte Carlo description of each feature in the data is correct

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SLIDE 9

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Evaluating the EM+JES

◮ overall strategy: evaluate the JES by roughly factorizing the components of EM+JES, and

verifying that the Monte Carlo description of each feature in the data is correct

◮ thus, the role of the in situ measurements in setting the scale is to provide systematic

uncertainties in situ measurement JES uncertainty component E/p single particle response central calorimeter response dijet relative calibration extrapolation to endcap and forward region Etower & track-jets multiple interactions In Situ Results:

(EM+JES) [GeV]

T

jet p 20 30 40 100 200 300 1000 jet energy scale 0.96 0.98 1 1.02 1.04 1.06 , R=0.6, TopoCluster

T

anti-k |<0.3 η 0.0<| global energy scale

ATLAS Preliminary

JES method: jet decomposition response convolution

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SLIDE 10

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Evaluating the EM+JES

◮ overall strategy: evaluate the JES by roughly factorizing the components of EM+JES, and

verifying that the Monte Carlo description of each feature in the data is correct

◮ thus, the role of the in situ measurements in setting the scale is to provide systematic

uncertainties in situ measurement JES uncertainty component E/p single particle response central calorimeter response dijet relative calibration extrapolation to endcap and forward region Etower & track-jets multiple interactions In Situ Results:

(EM+JES) [GeV]

T

jet p 20 30 40 100 200 300 1000 jet energy scale 0.96 0.98 1 1.02 1.04 1.06 , R=0.6, TopoCluster

T

anti-k |<0.3 η 0.0<| global energy scale

ATLAS Preliminary

JES method: jet decomposition response convolution

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SLIDE 11

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Evaluating the EM+JES

◮ overall strategy: evaluate the JES by roughly factorizing the components of EM+JES, and

verifying that the Monte Carlo description of each feature in the data is correct

◮ thus, the role of the in situ measurements in setting the scale is to provide systematic

uncertainties in situ measurement JES uncertainty component E/p single particle response central calorimeter response dijet relative calibration extrapolation to endcap and forward region Etower & track-jets multiple interactions In Situ Results:

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SLIDE 12

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

JES Summary

[GeV]

jet T

p

2

10

3

10 Data / MC 0.9 0.92 0.94 0.96 0.98 1 1.02 1.04 1.06 1.08 1.1 1.12 1.14 Multi-jet Track-jet

  • jet direct balance

γ

  • jet MPF

γ JES uncertainty =0.6, EM+JES R

t

anti-k ATLAS Preliminary

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SLIDE 13

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Summary

  • 1. using a scheme based on single particle response, ATLAS has developed a

defensible 3% uncertainty on the jet energy scale in the central barrel region

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SLIDE 14

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Summary

  • 1. using a scheme based on single particle response, ATLAS has developed a

defensible 3% uncertainty on the jet energy scale in the central barrel region

  • 2. multiple, independent cross-checks confirm this uncertainty

◮ γ + jet (MPF, direct pT balance) ◮ track ↔ calorimeter jet comparison ◮ multi-jet pT balancing

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SLIDE 15

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Summary

  • 1. using a scheme based on single particle response, ATLAS has developed a

defensible 3% uncertainty on the jet energy scale in the central barrel region

  • 2. multiple, independent cross-checks confirm this uncertainty

◮ γ + jet (MPF, direct pT balance) ◮ track ↔ calorimeter jet comparison ◮ multi-jet pT balancing

  • 3. local calibration scheme has been commissioned

◮ results for local and sequential schemes already tested at jet level, and show

good resolution improvement

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Introductary Remarks Jet Energy Scale Conclusions Extra Slides

EXTRA SLIDES

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Introductary Remarks Jet Energy Scale Conclusions Extra Slides

References

  • 1. Jet energy scale and its systematic uncertainty in proton-proton collisions at sqrt(s)=7 TeV

in ATLAS 2010 data, ATLAS-CONF-2011-032, 22 March 2011

  • 2. Determination of the ATLAS jet energy measurement uncertainty using photon-jet events in

proton-proton collisions at sqrt(s) = 7 TeV, ATLAS-CONF-2011-031, 18 March 2011

  • 3. In-situ jet energy scale and jet shape corrections for multiple interactions in the first ATLAS

data at the LHC, ATLAS-CONF-2011-030, 22 March 2011

  • 4. Probing the jet energy measurement at the TeV-scale with the multi-jet balance technique in

proton-proton collisions at sqrt(s)=7 TeV with the ATLAS detector, ATLAS-CONF-2011-029, 16 March 2011

  • 5. ATLAS Calorimeter Response to Single Isolated Hadrons and Estimation of the Calorimeter

Jet Scale Uncertainty, ATLAS-CONF-2011-028, 20 March 2011

  • 6. In-situ pseudorapidity intercalibration for evaluation of jet energy scale uncertainty using dijet

events in proton-proton collisions at sqrt(s) = 7 TeV, ATLAS-CONF-2011-014, 10 March 2011

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SLIDE 18

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Ingredients & Definitions

The goal of the JES calibration is to correct E and p of jets measured in the calorimeter to the corresponding truth reference jets. Ingredients

◮ response non-compensation (e/h > 1.3 in ATLAS) ◮ inactive regions, leakage, and punch through ◮ calorimeter signal definition (noise thresholds, jet width parameter)

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SLIDE 19

Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Ingredients & Definitions

The goal of the JES calibration is to correct E and p of jets measured in the calorimeter to the corresponding truth reference jets. Ingredients

◮ response non-compensation (e/h > 1.3 in ATLAS) ◮ inactive regions, leakage, and punch through ◮ calorimeter signal definition (noise thresholds, jet width parameter)

Definitions

◮ the JES is defined for a particular class of “nominal” jetsa: ◮ in QCD dijet events (mostly jets from gluons) ◮ isolated jets: ∆R(jeti , jetj=i ) > 2.0 ◮ nominal pileup scenario: NPV = 1 ◮ and with respect to a particular truth reference: ◮ jets from final state, stable particlesb excepting µ’s and ν’s ◮ matched to measured jets in ∆R < 0.3 aunless otherwise specified, all results shown are for jets defined with the anti-kT algorithm[?], with a width

parameter D = 0.6, built from 4/2/0 topological clusters

bstable is defined as τ > 10 ps

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Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Components of JES Uncertainty from Single Particle Response

[GeV]

T

jet p 20 30 100 200 1000 2000 relative calorimeter jet response 0.97 0.98 0.99 1 1.01 1.02 1.03 |<0.3 η 0.0<| , R=0.6, TopoCluster

t

anti-k E/p response ATLAS Preliminary [GeV]

T

jet p 20 30 100 200 1000 2000 relative calorimeter jet response 0.97 0.98 0.99 1 1.01 1.02 1.03 |<0.3 η 0.0<| , R=0.6, TopoCluster

t

anti-k threshold effects ATLAS Preliminary [GeV]

T

jet p 20 30 100 200 1000 2000 relative calorimeter jet response 0.97 0.98 0.99 1 1.01 1.02 1.03 |<0.3 η 0.0<| , R=0.6, TopoCluster

t

anti-k neutral hadrons ATLAS Preliminary [GeV]

T

jet p 20 30 100 200 1000 2000 relative calorimeter jet response 0.97 0.98 0.99 1 1.01 1.02 1.03 |<0.3 η 0.0<| , R=0.6, TopoCluster

t

anti-k E/p acceptance ATLAS Preliminary [GeV]

T

jet p 20 30 100 200 1000 2000 relative calorimeter jet response 0.97 0.98 0.99 1 1.01 1.02 1.03 |<0.3 η 0.0<| , R=0.6, TopoCluster

t

anti-k CTB response ATLAS Preliminary [GeV]

T

jet p 20 30 100 200 1000 2000 relative calorimeter jet response 0.97 0.98 0.99 1 1.01 1.02 1.03 |<0.3 η 0.0<| , R=0.6, TopoCluster

t

anti-k global energy scale ATLAS Preliminary

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Introductary Remarks Jet Energy Scale Conclusions Extra Slides

Extra Plots

jet

R 0.6 0.8 1

MPF EM scale, all jet algorithms < 60 GeV

γ T

45 < p Data PYTHIA

ATLAS Preliminary

  • 1

= 38 pb dt L

∫

= 7 TeV s

|

jet

η |

0.5 1

Data / MC 0.9 0.95 1 1.05 1.1

[GeV]

γ T

p 100 200

MC

/R

Data

R 0.9 0.95 1 1.05 1.1 1.15

MPF LCW, all jet algorithms Uncertainty Statistical Systematic Total

ATLAS Preliminary

  • 1

= 38 pb dt L

∫

= 7 TeV s

Validating JES in η with MPF (left) and other calibration scheme, based on local hadronic response correction (right).