Introduction Introduction Week of Jets Week of Jets FNAL, Aug. 24-28, 2009 FNAL, Aug. 24-28, 2009 Aug 23, 2009 Aug 23, 2009 Introduction To Jet Reconstruction In ATLAS Peter Loch Peter Loch University of Arizona University of Arizona Tucson, Arizona Tucson, Arizona USA USA
21
Embed
Introduction Week of Jets FNAL, Aug. 24-28, 2009 Aug 23, 2009 Introduction To Jet Reconstruction In ATLAS Peter Loch University of Arizona Tucson, Arizona.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
Aug 23, 2009Aug 23, 2009
Introduction To Jet Reconstruction In ATLAS
Introduction To Jet Reconstruction In ATLAS
Peter LochPeter Loch
University of ArizonaUniversity of Arizona
Tucson, ArizonaTucson, Arizona
USAUSA
Peter LochPeter Loch
University of ArizonaUniversity of Arizona
Tucson, ArizonaTucson, Arizona
USAUSA
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
2P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009My Road To Jets @ LHC
Started with calorimeter construction for H1/HERA (1987-1989)…Started with calorimeter construction for H1/HERA (1987-1989)… The “hardware years”…The “hardware years”…
……then Deep Inelastic Scattering with H1 (1989-1992,1993-1995)then Deep Inelastic Scattering with H1 (1989-1992,1993-1995) Electron, hadron, and jet reconstruction and calibration in a non-compensating calorimeter Electron, hadron, and jet reconstruction and calibration in a non-compensating calorimeter
Have always been attracted by complex response!Have always been attracted by complex response!
Experimental sensitivities to jet propertiesExperimental sensitivities to jet properties We did not call it sub-structure then!We did not call it sub-structure then!
Forward hadronic energy flow and jet productionForward hadronic energy flow and jet production E.g., DGLAP vs BFKL evolution at low Bjorken-E.g., DGLAP vs BFKL evolution at low Bjorken-xx
……with a short stop at DZero/Tevatron (1992)…with a short stop at DZero/Tevatron (1992)… Calorimeter response to minimum biasCalorimeter response to minimum bias
Mostly detector oriented noise, alignment and beam position studies Mostly detector oriented noise, alignment and beam position studies
……and at GEM/SSC (1992-1993)…and at GEM/SSC (1992-1993)… Design and response evaluation of the forward calorimeterDesign and response evaluation of the forward calorimeter
Detector prototyping and test beamsDetector prototyping and test beams
……and a long tenure in ATLAS/LHC (since 1995)and a long tenure in ATLAS/LHC (since 1995) Design and response evaluation of the forward calorimeterDesign and response evaluation of the forward calorimeter
Yes, it is the same design as for GEMYes, it is the same design as for GEM
Forward calorimeter detector construction managementForward calorimeter detector construction management My “Microsoft years”My “Microsoft years”
Focus on preparation for physics at LHC (since 2002)Focus on preparation for physics at LHC (since 2002) Initial interest jet physics and QCD…Initial interest jet physics and QCD…
Some leadershipSome leadership Calorimeter software coordination Calorimeter software coordination Jet and missing Et reconstruction performance coordinationJet and missing Et reconstruction performance coordination
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
3P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
Change of compositionChange of composition Radiation and decay inside Radiation and decay inside
detector volumedetector volume ““Randomization” of original Randomization” of original
particle contentparticle content Defocusing changes shape in Defocusing changes shape in
lab framelab frame Charged particles bend in Charged particles bend in
solenoid fieldsolenoid field Attenuation changes energyAttenuation changes energy
Total loss of soft charged Total loss of soft charged particles in magnetic fieldparticles in magnetic field
Partial and total energy loss of Partial and total energy loss of charged and neutral particles in charged and neutral particles in inactive upstream materialinactive upstream material
Hadronic and electromagnetic Hadronic and electromagnetic cacades in calorimeterscacades in calorimeters Distribute energy spatiallyDistribute energy spatially Lateral particle shower overlapLateral particle shower overlap
—
+
—
+
+—
+
100 MeV100 MeV
10 GeV10 GeV
1 GeV1 GeV
η
φ
Image of Jet in the Detector
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
4P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
+
—
+—
—
+
+
Change of compositionChange of composition Radiation and decay inside Radiation and decay inside
detector volumedetector volume ““Randomization” of original Randomization” of original
particle contentparticle content Defocusing changes shape in Defocusing changes shape in
lab framelab frame Charged particles bend in Charged particles bend in
solenoid fieldsolenoid field Attenuation changes energyAttenuation changes energy
Total loss of soft charged Total loss of soft charged particles in magnetic fieldparticles in magnetic field
Partial and total energy loss of Partial and total energy loss of charged and neutral particles in charged and neutral particles in inactive upstream materialinactive upstream material
Hadronic and electromagnetic Hadronic and electromagnetic cacades in calorimeterscacades in calorimeters Distribute energy spatiallyDistribute energy spatially Lateral particle shower overlapLateral particle shower overlap
100 MeV100 MeV
10 GeV10 GeV
1 GeV1 GeV
η
φ
Image of Jet in the Detector
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
5P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
+
—
+—
—
+
+
Change of compositionChange of composition Radiation and decay inside Radiation and decay inside
detector volumedetector volume ““Randomization” of original Randomization” of original
particle contentparticle content Defocusing changes shape in Defocusing changes shape in
lab framelab frame Charged particles bend in Charged particles bend in
solenoid fieldsolenoid field Attenuation changes energyAttenuation changes energy
Total loss of soft charged Total loss of soft charged particles in magnetic fieldparticles in magnetic field
Partial and total energy loss of Partial and total energy loss of charged and neutral particles in charged and neutral particles in inactive upstream materialinactive upstream material
Hadronic and electromagnetic Hadronic and electromagnetic cacades in calorimeterscacades in calorimeters Distribute energy spatiallyDistribute energy spatially Lateral particle shower overlapLateral particle shower overlap
100 MeV100 MeV
10 GeV10 GeV
1 GeV1 GeV
η
φ
Image of Jet in the Detector
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
6P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
+
—
+—
—
+
+
Change of compositionChange of composition Radiation and decay inside Radiation and decay inside
detector volumedetector volume ““Randomization” of original Randomization” of original
particle contentparticle content Defocusing changes shape in Defocusing changes shape in
lab framelab frame Charged particles bend in Charged particles bend in
solenoid fieldsolenoid field Attenuation changes energyAttenuation changes energy
Total loss of soft charged Total loss of soft charged particles in magnetic fieldparticles in magnetic field
Partial and total energy loss of Partial and total energy loss of charged and neutral particles in charged and neutral particles in inactive upstream materialinactive upstream material
Hadronic and electromagnetic Hadronic and electromagnetic cacades in calorimeterscacades in calorimeters Distribute energy spatiallyDistribute energy spatially Lateral particle shower overlapLateral particle shower overlap
+—
—
+
+
100 MeV100 MeV
10 GeV10 GeV
1 GeV1 GeV
η
φ
Image of Jet in the Detector
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
7P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
Change of compositionChange of composition Radiation and decay inside Radiation and decay inside
detector volumedetector volume ““Randomization” of original Randomization” of original
particle contentparticle content Defocusing changes shape in Defocusing changes shape in
lab framelab frame Charged particles bend in Charged particles bend in
solenoid fieldsolenoid field Attenuation changes energyAttenuation changes energy
Total loss of soft charged Total loss of soft charged particles in magnetic fieldparticles in magnetic field
Partial and total energy loss of Partial and total energy loss of charged and neutral particles in charged and neutral particles in inactive upstream materialinactive upstream material
Hadronic and electromagnetic Hadronic and electromagnetic cacades in calorimeterscacades in calorimeters Distribute energy spatiallyDistribute energy spatially Lateral particle shower overlapLateral particle shower overlap
Move to better motivated jet algorithmsMove to better motivated jet algorithms ATLAS uses FastJet and SISCone librariesATLAS uses FastJet and SISCone libraries
Common implementation theory/CMS/ATLAS Common implementation theory/CMS/ATLAS
Narrow (0.4) AntiKt jets preferred for initial physics Narrow (0.4) AntiKt jets preferred for initial physics Most regularly shapedMost regularly shaped More straight forward handle on extra energy from pile-up (?)More straight forward handle on extra energy from pile-up (?)
Legacy (ATLAS) seeded fixed cone still availableLegacy (ATLAS) seeded fixed cone still available Usefulness basically limited to LO final statesUsefulness basically limited to LO final states Fast algorithm ok for trigger and event filterFast algorithm ok for trigger and event filter
Factorized reconstructionFactorized reconstruction Attempt to use calorimeter signal definitions to address most detector Attempt to use calorimeter signal definitions to address most detector
specific issuesspecific issues Use towers and clustersUse towers and clusters
Calibrations and corrections determined independentlyCalibrations and corrections determined independently Distinguish carefully between relative and absolute corrections by least Distinguish carefully between relative and absolute corrections by least
interdependencyinterdependency Jet energy scale evolution
Limit to factorization introduced by calorimeterLimit to factorization introduced by calorimeter E.g. detector couples response and fragmentation – corrections often only possible on
average
More details on Thursday!More details on Thursday!
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
10P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009First Data Jet Calibration Priorities
calo signals
calot t
tjetcalo
t
p p
pR
p
1.6 2.4 GeVTp 1.6 2.4 GeVTp
single simulations
extracted from minbias
(plots from CERN-OPEN-2008-020)
Need flat jet response rather quicklyNeed flat jet response rather quickly Basis for first physics analysesBasis for first physics analyses
Systematics can dominate total error Systematics can dominate total error already at 10-200 pbalready at 10-200 pb-1-1
Depending on final state, kinematic range Depending on final state, kinematic range considered, fiducial cuts,…considered, fiducial cuts,…
Requires understanding of hadronic Requires understanding of hadronic responseresponse Minimum biasMinimum bias
Single charged hadron response of calorimeterSingle charged hadron response of calorimeter Pile-up with tracks and clustersPile-up with tracks and clusters
Di-jetsDi-jets Underlying event with tracks and clustersUnderlying event with tracks and clusters Direction dependent response correctionsDirection dependent response corrections
Prompt photonsPrompt photons Absolute scale by balancing, missing Et Absolute scale by balancing, missing Et
projection fraction, etc.projection fraction, etc.
Initial focus on simple approachesInitial focus on simple approaches Least number of algorithmsLeast number of algorithms Least numerical complexityLeast numerical complexity Realistic systematic error evaluationRealistic systematic error evaluation
Conservative ok for first data!Conservative ok for first data!
But also try new or alternative But also try new or alternative approaches!approaches!
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
11P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Initial Jet Calibration Scheme
optional
data driven
MC
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
12P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Beyond First Physics
Initial tasks focus on jet energy scale (JES) Initial tasks focus on jet energy scale (JES) errorserrors Binds most of the manpower todayBinds most of the manpower today
Rather wide spectrum of signal and calibration choices Rather wide spectrum of signal and calibration choices But did not want to make hard decisions based on MC alone!But did not want to make hard decisions based on MC alone!
Future activity more focused on jet featuresFuture activity more focused on jet features Jet-by-jet corrections to reduced fluctuations of JESJet-by-jet corrections to reduced fluctuations of JES
Attempt to unfold residual fragmentation dependenciesAttempt to unfold residual fragmentation dependencies Useful observables include jet shapes Useful observables include jet shapes
Jet-by-jet pile-up suppression Jet-by-jet pile-up suppression Qualitative change from initial run scenariosQualitative change from initial run scenarios
Pile-up signal history (= noise in ATLAS) depends on instantaneous luminosity and bunch crossing frequency
Large source of signal fluctuations affects all jet final statesLarge source of signal fluctuations affects all jet final states Experimental resolution for jet masses and substructureExperimental resolution for jet masses and substructure
Discovery tool for heavy particle decaysDiscovery tool for heavy particle decays E.g., fully hadronic decay of boosted top (“3 in 1”)
Experimentally challenging but not impossibleExperimentally challenging but not impossible (more on Wednesday & Thursday)
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
13P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
Multiple interactions Multiple interactions between partons in other between partons in other protons in the same protons in the same bunch crossingbunch crossing Consequence of high rate Consequence of high rate
(luminosity) and high (luminosity) and high proton-proton total cross-proton-proton total cross-section (~75 mb)section (~75 mb)
Statistically independent Statistically independent of hard scatteringof hard scattering Similar models used for soft Similar models used for soft
physics as in underlying physics as in underlying eventevent
Signal history in Signal history in calorimeter increases calorimeter increases noisenoise Signal 10-20 times slower Signal 10-20 times slower
(ATLAS) than bunch (ATLAS) than bunch crossing rate (25 ns)crossing rate (25 ns)
Noise has coherent Noise has coherent charactercharacter Cell signals linked through Cell signals linked through
past shower developmentspast shower developments
Et ~ 58 GeV
Et ~ 81 GeV
without pile-up
Pile-Up
Prog.Part.Nucl.Phys.60:484-551,2008
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
14P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
Multiple interactions Multiple interactions between partons in other between partons in other protons in the same protons in the same bunch crossingbunch crossing Consequence of high rate Consequence of high rate
(luminosity) and high (luminosity) and high proton-proton total cross-proton-proton total cross-section (~75 mb)section (~75 mb)
Statistically independent Statistically independent of hard scatteringof hard scattering Similar models used for soft Similar models used for soft
physics as in underlying physics as in underlying eventevent
Signal history in Signal history in calorimeter increases calorimeter increases noisenoise Signal 10-20 times slower Signal 10-20 times slower
(ATLAS) than bunch (ATLAS) than bunch crossing rate (25 ns)crossing rate (25 ns)
Noise has coherent Noise has coherent charactercharacter Cell signals linked through Cell signals linked through
past shower developmentspast shower developments
Et ~ 58 GeV
Et ~ 81 GeV
with design luminosity pile-up
Pile-Up
Prog.Part.Nucl.Phys.60:484-551,2008
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
15P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009
Multiple interactions Multiple interactions between partons in other between partons in other protons in the same protons in the same bunch crossingbunch crossing Consequence of high rate Consequence of high rate
(luminosity) and high (luminosity) and high proton-proton total cross-proton-proton total cross-section (~75 mb)section (~75 mb)
Statistically independent Statistically independent of hard scatteringof hard scattering Similar models used for soft Similar models used for soft
physics as in underlying physics as in underlying eventevent
Signal history in Signal history in calorimeter increases calorimeter increases noisenoise Signal 10-20 times slower Signal 10-20 times slower
(ATLAS) than bunch (ATLAS) than bunch crossing rate (25 ns)crossing rate (25 ns)
Noise has coherent Noise has coherent charactercharacter Cell signals linked through Cell signals linked through
past shower developmentspast shower developments
34 2 110 cm sL 34 2 110 cm sL
8 GeV
0.4R
0.7R
18 GeV
0.1 0.1 R
( ) (GeV)TRMS p
Pile-Up
Prog.Part.Nucl.Phys.60:484-551,2008
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
16P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009ATLAS Status
ATLAS is up and runningATLAS is up and running Used the LHC delay for continued sub-detector Used the LHC delay for continued sub-detector
commissioning and repaircommissioning and repair Cosmics for long term signal stability estimates and detector Cosmics for long term signal stability estimates and detector
timing and alignmenttiming and alignment Understanding of calorimeter noise with random (“empty”) Understanding of calorimeter noise with random (“empty”)
eventsevents Millions of cosmics recordedMillions of cosmics recorded
Test of computing chainTest of computing chain Re-reconstruction of cosmics trains ATLAS world wide Re-reconstruction of cosmics trains ATLAS world wide
computingcomputing
Some initial impressions for jets and missing Some initial impressions for jets and missing EtEt Noise contributions to missing Et reconstruction in random Noise contributions to missing Et reconstruction in random
eventsevents Calorimeter signal definition evaluationCalorimeter signal definition evaluation
Jets in cosmicsJets in cosmics Helps develop in-time background suppression strategiesHelps develop in-time background suppression strategies
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
17P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Cosmics In ATLAS
Single cosmic muons traversing the Single cosmic muons traversing the experiment help understanding experiment help understanding mostly timing and detector mostly timing and detector sensitivitiessensitivities
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
18P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Cosmic Showers In ATLAS
Cosmic showers hitting the detector Cosmic showers hitting the detector help understanding fake jet rates help understanding fake jet rates from this background in collision from this background in collision physicsphysics
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
19P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Understanding Cosmics
20 GeV
ATLAS Cone 0.4
(electromagnetic energy scale)
jett
cone
E
R
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
20P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Understanding Noise
The scalar missing Et sum is a very powerful diagnostic variable in random events (stability with time, noise suppression, major detector faults…)
Intr
od
ucti
on
In
trod
ucti
on
Week o
f Je
tsW
eek o
f Je
ts
FN
AL,
Au
g.
24
-28
, 20
09
FN
AL,
Au
g.
24
-28
, 20
09
21P. LochP. Loch
U of ArizonaU of Arizona
Aug 23, 2009Aug 23, 2009Conclusion & Outlook
ATLAS is ready for collisionsATLAS is ready for collisions The detector is operating since ~1 year The detector is operating since ~1 year
Major faults detected in 2008 are repairedMajor faults detected in 2008 are repaired Calorimeter noise is well understoodCalorimeter noise is well understood
Response to cosmics can be simulated reasonably wellResponse to cosmics can be simulated reasonably well First algorithms for suppression of cosmic background First algorithms for suppression of cosmic background
availableavailable New studies with overlaying simulated signal events with New studies with overlaying simulated signal events with
real cosmics underwayreal cosmics underway
More on ATLAS this weekMore on ATLAS this week Wednesday Wednesday
Experimental aspects of jet reconstruction in new physics Experimental aspects of jet reconstruction in new physics (informal)(informal) Jet masses, shapes, topologies, missing Et in ATLAS,…
ThursdayThursday Talk on “Jet Reconstruction in ATLAS” Talk on “Jet Reconstruction in ATLAS”
More details on calorimeter signals, algorithms, performance expectations, jet shapes,…