DILEPTON TRIGGERS for SUSY SEARCHES @ CDF

January 19, 2004January 19, 2004 11

Melisa RossiMelisa Rossi

Università degli Studi di Udine & INFNUniversità degli Studi di Udine & INFN

DILEPTON TRIGGERS for DILEPTON TRIGGERS for SUSY SEARCHES @ CDFSUSY SEARCHES @ CDF


OutlineOutline Physics MotivationPhysics Motivation

What is the Standard Model?What is the Standard Model? What is SUSY?What is SUSY? SUSY Lepton-based signaturesSUSY Lepton-based signatures

Tevatron Collider & CDF DetectorTevatron Collider & CDF Detector CDF Trigger SystemCDF Trigger System SUSY DILEPTON Trigger SUSY DILEPTON Trigger

StrategyStrategy StructureStructure

Trigger MonitoringTrigger Monitoring Monitoring variableMonitoring variable Good run listGood run list

Trigger studiesTrigger studies ConclusionsConclusions


What is the Standard Model ?What is the Standard Model ?

Very successful at describing dataVery successful at describing data Still unanswered questionsStill unanswered questions

Where does mass comes from?Where does mass comes from? What about gravity?What about gravity? What is the dark matter origin?What is the dark matter origin?

An effective low energy theory thatdescribes matter and its interactionscombines Strong, Weak and Electromagnetic interactions

▬▬► Beyond the Standard Model


What is SUSYWhat is SUSY Possible extension of the Standard ModelPossible extension of the Standard Model Additional symmetry between fermions and bosonsAdditional symmetry between fermions and bosons

SM fermion field SM fermion field supersymmetric boson field supersymmetric boson field

SM boson field SM boson field supersymmetric fermion field supersymmetric fermion field

Particle spectrum more than doublesParticle spectrum more than doubles

Fermions LeptonsQuarks

----------------------Gluon

----------------------Gauge Bosons

PhotonW,Z

Higgs

SfermionsSleptonsSquarks

--------------------Gluino

--------------------Gauginos

Neutralinos Charginos


What is SUSYWhat is SUSY

If SUSY was an exact symmetryIf SUSY was an exact symmetry SM particle mass = corresponding superpartner massSM particle mass = corresponding superpartner mass Clearly not realisticClearly not realistic

No sparticles have been observed so far No sparticles have been observed so far

Hence supersymmetry must be brokenHence supersymmetry must be broken The simplest realistic supersymmetric field theory is MSSMThe simplest realistic supersymmetric field theory is MSSM

Satisfies all phenomenological constraintsSatisfies all phenomenological constraints Depends on more than 100 parametersDepends on more than 100 parameters

Models to reduce the number of free parameters in SUSYModels to reduce the number of free parameters in SUSY cMSSM, mSUGRA...cMSSM, mSUGRA...

Different points in the SUSY parameter space lead to Different points in the SUSY parameter space lead to different phenomenologydifferent phenomenology


What is SUSYWhat is SUSY

SUSY introduces a new quantum numberSUSY introduces a new quantum number R-parity: 1 for particle, -1 for sparticleR-parity: 1 for particle, -1 for sparticle

In many models R-parity is conservedIn many models R-parity is conserved sparticles are producted in pairsparticles are producted in pair Lighest superparticle is stable (LSP)Lighest superparticle is stable (LSP)

LSP behaves like a heavy neutrinoLSP behaves like a heavy neutrino Not detectable: carrying away some energy and momentumNot detectable: carrying away some energy and momentum

SUSY processes result in final states with LPSSUSY processes result in final states with LPS SUSY events characterized by missing energySUSY events characterized by missing energy


What is SUSYWhat is SUSY ASSUMING SUSY

LSP is an excellent candidate for cold dark matterLSP is an excellent candidate for cold dark matter Coupling constants can unify at GUT scaleCoupling constants can unify at GUT scale


SUSY Lepton-based SignaturesSUSY Lepton-based Signatures

Chargino-neutralino associated productionChargino-neutralino associated production

Trilepton-basedTrilepton-based mSUGRA prediction at reachmSUGRA prediction at reach

Like-sign dileptonsLike-sign dileptons Release third lepton requestRelease third lepton request

Increase acceptanceIncrease acceptance LS requirement for background rejectionLS requirement for background rejection

0 0 02 1 1 1pp


SUSY Lepton-based SignaturesSUSY Lepton-based Signatures

Signatures characterized bySignatures characterized by Multiple leptons Multiple leptons

relatively low prelatively low pTT (<20GeV/c (<20GeV/c22)) Missing Et from multiple sourcesMissing Et from multiple sources

Moderate missing EtModerate missing Et (need full understanding of the detector)(need full understanding of the detector)

Lepton-based Signatures very clean. This is particularly Lepton-based Signatures very clean. This is particularly useful at hadron collider where QCD background is large.useful at hadron collider where QCD background is large.

m0 = 100 GeV,

m1/2 = 180 GeV,

A0 =0,

tanβ=3,

sgn>0

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Tevatron Collider Tevatron Collider

RunI (1992-1996)RunI (1992-1996) ppbar ppbar √s = √s = 1.8 TeV1.8 TeV luminosity peak ~1.5E31cmluminosity peak ~1.5E31cm-2-2ss-1-1

6x6 bunches6x6 bunches bunch crossing every 3.5bunch crossing every 3.5μμss

RunII (since 2001)RunII (since 2001) ppbar ppbar √s = √s = 1.96 TeV1.96 TeV luminosity peak ~1E32cmluminosity peak ~1E32cm-2-2ss-1-1

36x36 bunches36x36 bunches bunch crossing every 396nsbunch crossing every 396ns

6.3 km ring for a proton-antiproton collider with 980 Gev/beam

Tevatron

Main injector & recycler

CDF D0

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Tevatron LuminosityTevatron Luminosity

Excellent performance in 2004 for RunII

500 pb-1 delivered 350 pb-1 on tape 250 pb-1 analyzed (100pb-1 in RunI) 4-8 fb-1 by 2009

Plan for ~1.5E32cm–2s–1 luminosity peak by the end of 2005

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The CDF DetectorThe CDF Detector

Retained from RunI central and endwall calorimeter central muon system solenoid

New in RunII tracking system

central outer tracker (COT) silicon vertex detector (SVX+ISL)

Endplug calorimeter Muon system upgrade Front-end electronics DAQ/Trigger system

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CDF Trigger SystemCDF Trigger System TriggerTrigger

combines information from all subdetectorscombines information from all subdetectors (tracking, calorimeter, muon chambers...) (tracking, calorimeter, muon chambers...) takes online decision to keep or reject eventstakes online decision to keep or reject events

CDF Technical constrainsCDF Technical constrains Rate limitsRate limits

CDF developedCDF developed 3 level trigger system3 level trigger system organized inorganized in

Path = unique combination of L1,L2,L3Path = unique combination of L1,L2,L3 Dataset = combination of pathsDataset = combination of paths

L1trigger

L1trigger

L1trigger

L1trigger

L2trigger

L2trigger

L2trigger

L2trigger

L3trigger

L3trigger

L3trigger

L3trigger

Path 1 Path 2

DatasetDataset

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CDF Trigger SystemCDF Trigger System Accept rates are 10x higher than RunIAccept rates are 10x higher than RunI L1+L2 rejection factor is 20000:1L1+L2 rejection factor is 20000:1 The trigger budget is balanced The trigger budget is balanced

between all the physics groups between all the physics groups

(bandwidth distribution)(bandwidth distribution)

CDF Detector

OFFLINE

L1 pipeline5.5μs

L2 decision20μs

L3 decision600ms

7.6 million events/sec

50kHz

300Hz

75Hz

RateRate Cross Cross

Section Section

L1L1 50 kHz50 kHz 400 400 μμbb

L2L2 300 Hz300 Hz 3 3 μμbb

L3L3 75 Hz75 Hz 750nb750nb

Rate = Inst. Lumi. x cross section

@1E32cm–2s–1

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CDF Trigger SystemCDF Trigger System Level 1 informationLevel 1 information

CalorimeterCalorimeter trigger towers trigger towers ΔηΔη x x ΔφΔφ = 0.2 x 15 = 0.2 x 15 Global trigger: missing Et, SumEtGlobal trigger: missing Et, SumEt

Tracking (eXtremelyFastTracker)Tracking (eXtremelyFastTracker) Efficiency> 96% for pT>1.5GeV/cEfficiency> 96% for pT>1.5GeV/c

Muon = 2D track matched to stubMuon = 2D track matched to stub Stub = cluster of hits in muon Stub = cluster of hits in muon

chamberchamber Electron = 2D track matched to Electron = 2D track matched to

trigger towertrigger tower

Level 2 informationLevel 2 information Calorimeter clustering Calorimeter clustering

algorithmalgorithm Identify seed towersIdentify seed towers Identify shoulder towersIdentify shoulder towers

Silicon vertex trackerSilicon vertex tracker To identify displaced tracksTo identify displaced tracks Impact parameter resolution Impact parameter resolution

3535μμmm Muon boardsMuon boards

New L2 code in 2004New L2 code in 2004 Level 3 informationLevel 3 information

Offline-like reconstructionOffline-like reconstruction

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SUSY DILEPTON TriggerSUSY DILEPTON Trigger

SUSY Lepton-based signalsSUSY Lepton-based signals low pt multilepton final stateslow pt multilepton final states

Ideal choice would be an inclusive lepton triggerIdeal choice would be an inclusive lepton trigger CDF opted for a multipath DILEPTON triggerCDF opted for a multipath DILEPTON trigger

To fit with bandwidth available resourcesTo fit with bandwidth available resources To achieve the maximum acceptance/efficiencyTo achieve the maximum acceptance/efficiency

The SUSY DILEPTON Dataset

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Lepton types involved in the triggerLepton types involved in the trigger CEM4 central electron with 4GeV/c ptCEM4 central electron with 4GeV/c pt CEM8 central electron with 8GeV/c ptCEM8 central electron with 8GeV/c pt PEM8 forward electron with 8GeV/c etPEM8 forward electron with 8GeV/c et CMU4 muon with 4GeV/c pt (CMU4 muon with 4GeV/c pt (ηη<0.6)<0.6) CMUP4 muon with 4GeV/c pt (CMUP4 muon with 4GeV/c pt (ηη<0.6) <0.6) CMX4 muon with 4GeV/c pt (0.6<CMX4 muon with 4GeV/c pt (0.6<ηη<1)<1)

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Lepton types combined in 20 trigger pathsLepton types combined in 20 trigger paths

CEM4_CMU4CEM4_CMU4CEM4_CMUP4CEM4_CMUP4CEM4_CMX4CEM4_CMX4CEM4_PEM8CEM4_PEM8CMU4_PEM8CMU4_PEM8CMUP4_PEM8CMUP4_PEM8CEM4_CEM4CEM4_CEM4 ..............

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Trigger issues areTrigger issues are Monitoring generally a study for each path,Monitoring generally a study for each path, Calibration complex with a multipath structure!!Calibration complex with a multipath structure!!

We followed a We followed a new strategy new strategy to sto simplify calibrationimplify calibrationdefine a define a lepton objectlepton object for each lepton type for each lepton type

definitions do not depend on the specific pathdefinitions do not depend on the specific path

compute efficiency for each compute efficiency for each lepton objectlepton objectcombine combine lepton objectslepton objects into trigger paths into trigger paths

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20 trigger paths 6 lepton objects6 lepton objects

lepton object lepton object ==

standard single lepton definition @ trigger levelstandard single lepton definition @ trigger level

CEM4CEM4

CEM8CEM8

PEM8PEM8

CMU4CMU4

CMUP4CMUP4

CMX4CMX4

electrons

muons

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SUSY DILEPTON Trigger SUSY DILEPTON Trigger

SUSY Trigger organized in 3 categoriesSUSY Trigger organized in 3 categories A A : baseline paths: baseline paths

Ask for 2 leptons of 4GeV/c pt at L1, L2, L3Ask for 2 leptons of 4GeV/c pt at L1, L2, L3

BB : complementary paths : complementary paths Ask for 1 lepton + an additional track of 8 GeV/c pt at L1 and L2Ask for 1 lepton + an additional track of 8 GeV/c pt at L1 and L2 To recover stub/cluster inefficiencyTo recover stub/cluster inefficiency

C C : complementary paths: complementary paths Ask for 1 lepton of 12 GeV/c pt at L1 and L2 Ask for 1 lepton of 12 GeV/c pt at L1 and L2 To increase the acceptanceTo increase the acceptance

All paths contribute to the acceptanceAll paths contribute to the acceptance

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Trigger cross section: L2 700 nb L3 80 nb

SUSY DILEPTON Trigger SUSY DILEPTON Trigger

AA BB CC

L1L2L1L2 2 Low-pt leptons2 Low-pt leptons Medium-pt Medium-pt lepton+tracklepton+track

High-pt inclusive High-pt inclusive leptonlepton

L3L3 2 Low-pt leptons2 Low-pt leptons

@7.5E32cm–2s–1

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Trigger MonitoringTrigger Monitoring

Monitoring the performance of a trigger is Monitoring the performance of a trigger is importantimportant to check the quality of the collected eventsto check the quality of the collected events to verify the stability in time of the trigger responseto verify the stability in time of the trigger response to keep track of trigger changesto keep track of trigger changes

Need of a suitable Monitoring VariableNeed of a suitable Monitoring Variable

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Monitoring ApproachMonitoring Approach Consider events collected by each of the trigger pathConsider events collected by each of the trigger path Verify which leptons are reconstructed @ offline levelVerify which leptons are reconstructed @ offline level

For each trigger pathFor each trigger path

Trigger level Offline level Trigger level Offline level 2 lepton objects found 2 leptons 2 lepton objects found 2 leptons reconstructed reconstructed

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Trigger MonitoringTrigger Monitoring Each DILEPTON Trigger path requiresEach DILEPTON Trigger path requires

lepton1 & lepton2 @ trigger levellepton1 & lepton2 @ trigger level

For each trigger path:For each trigger path: DD1 1 = number of collected events = number of collected events NN11 = number of collected events with lepton 1 = number of collected events with lepton 1

reconstructed offlinereconstructed offline

and same quantities for lepton and same quantities for lepton 2 2

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Monitoring Variable: RMonitoring Variable: R

It separate information about lepton1 and lepton 2It separate information about lepton1 and lepton 2 It is a sort of purityIt is a sort of purity

0 < R < 10 < R < 1 higher R higher R higher quality of the collected events higher quality of the collected events

In ideal conditions R = 1 In ideal conditions R = 1

It is expected to be stable in timeIt is expected to be stable in time We have several R values for each lepton typeWe have several R values for each lepton type

expect no significant differences between different trigger paths expect no significant differences between different trigger paths

R1 = N1/D1 R2 = N2/D2

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PATH:CEM4_PEM8 PATH:CEM4_CMUP4

► R is locally stable in time► Steps in distribution correlated to trigger changes► changes increase R value higher quality► similar absolute R values for a given lepton type

R distribution vs. Time (run) for CEM4

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SUSY TRIGGER MonitoringSUSY TRIGGER Monitoring

R behaves as expectedR behaves as expected We can use it as discriminator for a good/bad runWe can use it as discriminator for a good/bad run

For each lepton objectFor each lepton object we define a suspect run we define a suspect run1.1. Test for R indipendence of trigger path Test for R indipendence of trigger path

2.2. Test for R stability in time Test for R stability in time

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Supect run definition for each lepton objectSupect run definition for each lepton object1.1. R indipendence of trigger pathR indipendence of trigger path

1.1. R = value for each trigger pathR = value for each trigger path

2.2. RRleptonlepton = average value for each run= average value for each run

3.3. The run is suspect if |R-The run is suspect if |R-RRleptonlepton| > 10| > 10σσ

2.2. R stabilityR stability1.1. <R<Rleptonlepton>> = = RRleptonlepton local average over 20 runs local average over 20 runs

2.2. The run is suspect if |The run is suspect if |RRleptonlepton--<R<Rleptonlepton>>| > 5| > 5σσ

Rlepton

run

R 11

2

2

run2 run3run1

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Suspect run luminosity Suspect run luminosity

for lepton object for lepton object

total suspect luminosity 37pb-1 out of 380 pb-1 considered

CEM4CEM4 0pb0pb-1-1

CEM8CEM8 5pb5pb-1-1

PEM8PEM8 7pb7pb-1-1

CMX4CMX4 30pb30pb-1-1

CMU4CMU4 5pb5pb-1-1

CMUP4CMUP4 1pb1pb-1-1

Rlepton stability

CEM4

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SUSY DILEPTON Trigger StudiesSUSY DILEPTON Trigger Studies

CDF is facing high luminosity scenariosCDF is facing high luminosity scenarios trigger cross sections depend on luminositytrigger cross sections depend on luminosity possible growth factor @ high luminosity possible growth factor @ high luminosity

For any process rate R = L For any process rate R = L σσ For a physics process For a physics process σσ independent of L independent of L For trigger cross sections, observe:For trigger cross sections, observe:

σσ = A / L + B + C L + D L = A / L + B + C L + D L22

Growth terms

Constant σConstant rate

Growth factor in trigger cross section

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For SUSY DILEPTON TriggerFor SUSY DILEPTON Trigger Possible large growth factor Possible large growth factor @ L2@ L2

In particular for complementary pathsIn particular for complementary paths

We performed a L2 StudyWe performed a L2 Study Total and exclusive cross section behaviour with luminosity Total and exclusive cross section behaviour with luminosity

SUSY DILEPTON Trigger StudiesSUSY DILEPTON Trigger Studies

exclusive cross section =effective cross section @ L2 w.r.t.

the whole CDF trigger

High-pt inclusive muon: L2_CMUP6_PT8 High-pt inclusive electron: L2_CEM12_PT8 Medium-pt electron+track: L2_CEM8_PT8_CES3_&_TRK8

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L2 X-SECTIONS (nb) vs. L2 X-SECTIONS (nb) vs. L (cmL (cm-2-2ss--

11))L2_CMUP6_PT8

Inclusive muon: No major growth factor Used by variety of physics group (not only exotic)

σTOT

σEX

L2_CEM8_PT8_CES3_&_TRK8

Electron+track: σTOT rises with L Adds very little to global L2 bandwidth

σTOT

σEX

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L2 X-SECTIONS (nb) vs. L2 X-SECTIONS (nb) vs. L (cmL (cm--

22ss-1-1))

Inclusive electron: No growth factor in σtot

σEX ≤ 100nb

L2_CEM12_PT8

σTOT

σEX

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Summary -1-Summary -1-

Physics motivation for SUSYPhysics motivation for SUSY multiple leptons final statesmultiple leptons final states

DILEPTON Trigger for SUSY @ CDFDILEPTON Trigger for SUSY @ CDFComplex Multipath triggerComplex Multipath trigger structure structure

New strategyNew strategyStandard Standard lepton objectlepton object definition definition

To simplify calibration and monitoringTo simplify calibration and monitoring

January 19, 2004January 19, 2004 3636


SUSY DILEPTON Trigger MonitoringSUSY DILEPTON Trigger MonitoringVariable choice: RVariable choice: R

gives information about event qualitygives information about event qualitybehaves as expectedbehaves as expected

locally stable in timelocally stable in time steps correlated to trigger changessteps correlated to trigger changes

Good run list per lepton object doneGood run list per lepton object done37pb of suspect luminosity (10% of the total)37pb of suspect luminosity (10% of the total)

Ready for Trigger CalibrationReady for Trigger Calibration

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SUSY DILEPTON trigger up to shutdown SUSY DILEPTON trigger up to shutdown ’04’04Complementary paths are healthyComplementary paths are healthy

No appreciable growth factorsNo appreciable growth factorsSmall effective cross sectionsSmall effective cross sections

CDF should be ready for CDF should be ready for 1.5E32cm1.5E32cm-2-2ss-1-1

the whole CDF trigger will be revisedthe whole CDF trigger will be revised need to re-think also the SUSY trigger for 2005 fallneed to re-think also the SUSY trigger for 2005 fall

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DILEPTON TRIGGERS for SUSY SEARCHES @ CDF