Concepts of Particle Detection Concepts of Particle Detection nd Id ntifi ti n (ID)nd Id ntifi ti n (ID)and Identification (ID)and Identification (ID)

PHYS 736(2009)

Teruki Kamon(2009)

How to identify the particles?

So far, my lectures are emphasized theinterconnection between particle physicsp p yand cosmology.

Let’s take moment to think about anexperimental particle physics aspectexperimental particle-physics aspect.Namely, how we are going to identify the SMparticles?

Particle Physics and Cosmology 22

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MISSING TRANSVERSE ENERGY TERUKITERUKI KAMONKAMON

((TAMU/ Fermilab / Kyungpook National Univ. )

OUTLINE1) “Why MET? - very exciting physics opportunities”1) Why MET? - very exciting physics opportunities

2) Concept of missing transverse energy (missing ETor MET) to infer the escaping particles - neutrinos,

CSI:CSI: METMET

or MET) to infer the escaping particles neutrinos,weakly interacting non-SM particles (e.g., SUSYdark matter particle), particles in very forwardregion (|�| > 5)CSI: CSI: METMET

CCollider ollider SScene cene IInvestigationnvestigation

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3) Three different techniques to calculate MET in CMS

4) Summary

if thi it i CMS HEP

12Aug 3, 2009 J Term IV : MET

… if you see this, it is a CMS or HEPjargon. Not in a physics textbook.

DISCOVERIES WITH “MET”Standard Model’s CV

1973 B S Neutral current1973 B.S. � Neutral current@ CERN SPS (400 GeV p)

1983 M.S. – “W/Z discovery” W� e�y@ CERN SppS (540 GeV )

1995 Ph.D. – “Top discovery”

pp_ W� e�

t � W b@ Fermilab Tevatron (1.8 TeV )

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MET MET -- inferring neutrinosinferring neutrinos

MET(& JETS) AT THE LHCMET(& JETS) AT THE LHC

Teruki Kamon J Term IV : MET 14MET MET -- inferring inferring newnew physics (e.g., Dark Matter)physics (e.g., Dark Matter)

E l SSUSSY ii h R ii CC iiMET(& JETS) AT THE LHCMET(& JETS) AT THE LHC

EExxaammppllee:: SSUUSSYY wwiitthh RR--ppaarriittyy CCoonnsseerrvvaattiioonn g~g~ , q~g~ , or q~q~ production will be dominant, followedgg , qg , qq p ,

by their decays (e.g., 02�~qq~ � ). � JJeettss

R parity conservation p y� Stable lightest supersymmetric particle (LSP)

� If LSP is the lightest neutralino ( 0�~ )� If LSP is the lightest neutralino ( 1� ), it will escape the detector � MMEETT (( TE ))

0~ C ld D k M tt did t � CC ll 01� = Cold Dark Matter candidate � CCoossmmoollooggyy

� Thus, the evidence of SUSY-like new physics will appearin the Jets+MET final statesin the Jets+MET final states.

CCoossmmoollooggyy ++ LLHHCC = [Exciting Motivation]++ [Right Place&Timing] [Exciting Motivation]+ [Right Place&Timing]

Teruki Kamon J Term IV : MET 15

STARTING WITH “TOWER” GEOMETRYSTARTING WITH “TOWER” GEOMETRYA design to measure the direction of energy flow

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A design to measure the direction of energy flow

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PARTICLE IDENTIFICATION (ID) PARTICLE IDENTIFICATION (ID) Identify all particles and measure their 4 vectorsIdentify all particles and measure their 4-vectors

Objectt ReconstructionObjectt Reconstruction Particlee IDParticlee ID PhysicsPhysics ObjectsObjectsObject ReconstructionObject Reconstruction Particle IDParticle ID PhysicsPhysics ObjectsObjects

Global muon reconstruction Muons

HCAL clusters w/ tracks Charged hadrons

ECAL clusters w/ tracks Electrons

HCAL clusters w/o tracks Neutral hadrons

ECALL l tt // t k Ph tECAL clusters w/o tracks Photons

HCAL, ECAL w/ tracks Quarks, gluons17Teruki Kamon J Term IV : MET

COLLISION, PRODUCTION, DECAYSCOLLISION, PRODUCTION, DECAYSpp pp

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“MET” CORRECTIONS“MET” CORRECTIONSMET ti t b i t th t lMET corrections are necessary to bring to the true value.

1)1) MuonMuon CorrectionCorrection� Replace muon calorimeter response with muon track

momentummomentum

2)2) JetJet EnergyEnergy ScaleScale (JES)(JES) CorrectionCorrection� Calibrate calorimeter towers (or cells) within jets as a� Calibrate calorimeter towers (or cells) within jets as a

function of �, pT, and EM fraction

3)3) UnclusteredUnclustered EnergyEnergy andand PilePile��upup CorrectionCorrection3)3) UnclusteredUnclustered EnergyEnergy andand PilePile upup CorrectionCorrection� Account for response variations due to unclustered

particles, soft particles, and double counting in JES from(i) underlying event (UE) and (ii) pile�up (PU).(i) underlying event (UE) and (ii) pile up (PU).

4)4) TauTau CorrectionCorrection� Account for difference in its energy scale between

Teruki Kamon J Term IV : MET 14

� Account for difference in its energy scale betweenhadronically�decaying taus and light�flavor jets

SEQUENCE OF MET CORRECTIONSSEQUENCE OF MET CORRECTIONSMET ti t b i t th t lMET corrections are necessary to bring to the true value:

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QCD P > 800 GeV with at least one global muon P > 10 GeVMUONMUON SELECTION FOR METSELECTION FOR MET

QCD PT > 800 GeV with at least one global muon PT > 10 GeV

With previousWith previous muonmuon selectionselection With presentWith present muonmuon selectionselection1

C t d fC t d f

With previous With previous muonmuon selectionselection With present With present muonmuon selectionselection

95% of global muons inQCDpt800 sample are fake!

Corrected for Corrected for JES && JES && muonsmuons

CorrectedCorrectedfor JES onlyfor JES only

Corrected forCorrected forJES && JES && muonsmuons

Corrected Corrected for JES onlyfor JES only

“good” muons“good” muons “fake” muons“fake” muons

MET (GeV) MET (GeV)

Global Global muonsmuons, no cuts, no cuts 100% 100%dd00 < 2 mm, number of hits > 10< 2 mm, number of hits > 10 96% 76%Must be a trackerMust be a tracker muonmuon 95% 27%

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Must be a tracker Must be a tracker muonmuon 95% 27%��22 cut (< 10)cut (< 10) 93% 9.7%

Teruki Kamon J Term IV : MET

MUONMUON, JETS, AND TAU CORRECTIONS, JETS, AND TAU CORRECTIONS2 41 2 4“Type I” = “Type I” = �� + JES+ JES

“Type II” = UE + PU“Type II” = UE + PUjet jet ""

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Calo MET+JES

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MET USING TRACKSMET USING TRACKSTrack Single Particle

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MET USING ALL SUBMET USING ALL SUB--DETECTORSDETECTORSParticle Flow Algorithm: Individual particles (e, �, , �, �, N0, V0, PU, NI)are reconstructed and identified by thoroughly exploiting thecharacteristics of all sub-detectors simultaneously. This algorithm willy gmaximize its efficiency, purity, and accuracy.

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ROBUSTNESSROBUSTNESSCaloMET, tcMET, and pfMET are conceptually different, but provide:1) respective performances with largely independent systematicuncertainties and different failure modes;

2) rapid understanding and a robust determination of the missingtransverse energy in CMS especially for the first collision data attransverse energy in CMS, especially for the first collision data atthe LHC.

caloMET(type 1) tcMET pfMET

Example [EWK-e group]: understanding the MET shape in dijet & �+jet events for $(W�e�)

Teruki Kamon J Term IV : MET 27

Alll MET-relatedd taskss aree interconnectedd withh DPGG POGG andd PAG

MET “EXERCISE” BOXESMET “EXERCISE” BOXESAll MET-related tasks are interconnected with DPG, POG and PAG.

Abnormal Cell HandlingAbnormal Cell Handling MET & MHT TriggersMET & MHT Triggers

Noise CleanupNoise Cleanup MET Trigger MonitoringMET Trigger MonitoringMET > 100 Express StreamMET > 100 Express Stream

MET Data Quality MonitoringMET Data Quality MonitoringCosmic Ray Cosmic Ray MuonMuon TagTagBeam Halo Beam Halo MuonMuon TagTag

�%�%//�� CalibrationCalibration

JESJES C tiC ti

METT Creation/CorrectionMETT Creation/Correction

JESJES CorrectionCorrection

METT Scalee Validationn METT Scalee Validationn MET Creation/CorrectionMET Creation/Correction•• CaloMETCaloMET, Type I (JES, mu), tau , Type II, Type I (JES, mu), tau , Type II•• MHTMHT•• TrackTrack--corrected MET corrected MET •• PFPF--METMET

MET Scale Validation MET Scale Validation with Datawith Data

•• No real MET sample: Z (�ll ) + jets•• Loww METT sample:: WW (�l� )) + jets

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PFPF METMET•• MET & MHT significancesMET & MHT significances•• Optimization of tower energy thresholdsOptimization of tower energy thresholds

Low MET sample: W (�l� ) jets•• Medium MET sample: t t• Explore new physics with high MET

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Filip Moortgat (filip.moortgat@cern.ch)Teruki Kamon (t-kamon@tamu.edu)

US CMS InstitutionsBrown, UC San Diego, UC Santa Barbara, UC Riverside, Cornell,

Teruki Kamon J Term IV : MET 29

Fermilab, Florida, U of Illinois at Chicago, Iowa, Maryland,Princeton, Rockefeller, Texas A&M, …

““SUPERSYMMETRISTSSUPERSYMMETRISTS, BEWARE!”, BEWARE!”

CERN-TH.3968/84

IS SUPERSYMMETRY FOUND?IS SUPERSYMMETRY FOUND?J. Ellis, SUSY07J. Ellis, SUSY07

Experimental Observation of Events with LargeLargeMissingMissing TransverseTransverse EnergyEnergy Accompanied By a Jet or

CERN-EP/84-4229 March 1984

Photon(s) in ppbar Collisions at /s = 540 GeV

Teruki Kamon J Term IV : MET

(submitted to Phys. Lett. B)

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