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Teilchen 2, 4. November 2005TSS: Triggering in ATLAS3 ATLAS TRIGGER MENU COVERAGE Inclusive and di-lepton B physics H SUSY, leptoquarks Resonances, compositeness Gauge boson pair production for study of anomalous couplings and behaviour of production at high energies single and pair top production direct Higgs production with H ZZ*/WW*; associated SM Higgs production with WH, ZH, ttH MSSM Higgs decays Production of new gauge bosons with decays to leptons. SUSY and leptoquark searches specialised, more exclusive menus 2EM15I at L1, 2 20i at L2. Also MSSM. High p T jets with/without E Tmiss. High p T jets. Triggering mostly with inclusive / di-leptons.
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TRIGGERING IN THE ATLAS
EXPERIMENT
Thomas Schörner-SadeniusUHH
Teilchenphysik II4. November 2005
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 2
PHYSICS AT THE LHC IIComparison of SM and ‘new physics’ processes
Small cross-sections for
‘new physics’processes
Understandingof SM processes
important
• Backgrounds for ‘discovery physics’: Wbb, ttbb, W/Z pairs…• Calibration, energy scale: Ze+e-,+-, J/e+e-,+-, Wjj…
At high luminosity~23 events overlaid
… for 2•1033cm-2s-1 usually only one event
… and small branching ratios (e.g. H).SM processes dominate.
Necessity of efficient trigger!
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 3
ATLAS TRIGGER MENU COVERAGE
Inclusive anddi-lepton
B physics
H
SUSY,leptoquarks
Resonances,compositeness
• Gauge boson pair production for study of anomalous couplings and behaviour of production at high energies • single and pair top production• direct Higgs production with HZZ*/WW*; associated SM Higgs production with WH, ZH, ttH• MSSM Higgs decays• Production of new gauge bosons with decays to leptons. • SUSY and leptoquark searches
• specialised, more exclusive menus
• 2EM15I at L1, 220i at L2. Also MSSM.
• High pT jets with/without ETmiss.
• High pT jets.
Triggering mostly with inclusive / di-leptons.
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 4
THE ATLAS EXPERIMENT - Length ~40 m- Diameter ~25 m- Weight ~7000 t- 108 channels (event ~2MB)
- ‘Inner (tracking) Detector’- calorimeters (energies)- muon detectors
- Barrel: solenoid around ID and toroid fields in muon system- Endcaps: toroid fields
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 5
THE ‘INNER DETECTOR’
Pixel Detector:
- 3 barrel layers - 2•4 end-discs - 140•106 channels- R=12m,z,R=~70m- || <2.5
Silicon Tracker:
- 4 barrel layers, || <1.4 - 2•9 end-discs, 1.4 < < 2.5- Area 60 m2
- 6.2•106 channels- R=16m, z,R=580m
Transition Radiation Tracker
- 0.42•106 channels- =170m per straw- || <2.5
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 6
THE CALORIMETERS
Hadronic Tile:- 463000 scintillating tiles- 10000 PMTs- Granularity 0.1•0.1 - : <1.0, (0.8-1.7)- L=11.4 m, Rout=4.2 m
Hadronic LArEndcaps:
- steel absorbers- 4400 channels- 0.1•0.1 / 0.2•0.2- 1-5
EM LAr Accordeon:
- lead absorbers- 174000 channels- 0.025•0.025- : <2.5, <3.2
Forward LAr:- 30000 rods of 1mm- cell size 2-5cm2 (4 rods)- : <3.1, <4.9- 1 copper, 2 tungsten
LAr Pre-SamplerAgainst effects of
energy losses in front of calorimeters
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 7
THE MUON SYSTEM
Monitored Drift Tubes
- 3 cylinders at R=7, 7.5, 10m- 3 layers at z=7, 10, 14 m- 372000 tubes, 70-630 cm- space=80m, t=300ps (24-bit FADCs)
Cathode Strip Chambers
- 67000 wires- only for ||>2 in first layer- space=60m, t=7ns
Thin Gap Chambers
- 440000 channels- ~MWPCs
Resistive Plate Chambers- 354000 channels- space=1cm- trigger signals in 1ns
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 8
THE ATLAS TRIGGER: OVERVIEWMulti-layer structure for rate reduction: 1 GHz 100 Hz.
} EF- Full event- Best calibration- Offline algorithms- Latency ~seconds
} L1
- Hardware-based (FPGAs and ASICs)- Coarse granularity from calo/muon- 2s latency (pipelines)
} L2
- ‘Regions-of-Interest’- ‘Fast rejection’- Spec. algorithms- Latency ~10ms
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 9
THE LEVEL1-TRIGGERSelection based on high-pT objects from calo and muon.
MultiplicitiesRegions-
of-InterestEvent decision
for L1
Interface tofront-end
Muoncandidatesabove pT
thresholds
Interface to highertrigger levels/DAQ:objects with pT,,
Candidates forelectrons/photons,taus/hadrons,jetsabove pT thres-holds.
Energy sumsabove thresholds
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 10
THE CALORIMETER TRIGGER II
Example: The /hadron trigger Example: The jet/energy trigger
• 2·2 jet EM+HA cluster (RoI) in 2·2 or 3·3 or 4·4 region (gives ET).
• 8 (4) (forward) jet ET thresholds.
• Total/missing ET from jets (sum of 0.2·0.2 jet elements to ·=0.4·0.2, conversion to Ex,Ey, then summation).
• Maximum of EM+HA ET in 2·2 ‘RoI’, isolation criteria (alternative core definitions?).
• Multiplicities for 8(8) e/ (/ hadron) ET thresholds.
Builds candidate objects (RoIs): electrons/photons, taus/hadrons, jets.Ideas about core definitions, isolation criteria not really finalised.
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 11
THE MUON TRIGGER
• ‘Roads’ can be defined for 6 different pT thresholds (for which multiplicity counts are delivered to the CTP).• BCID=1.5 ns.
Trigger chambers: • 3 RPC stations for ||<1.05• 3 TGC stations for 1.05<||<2.4. • 2 , layers per station (TGC 2/3)
pT information from hit coincidences in successive detector layers.
Procedure:• Put predefined ‘roads’ through all stations (width in ~ pT). • If hit coincidences in 2(3) stations muon candidate for pT thres- hold corresponding to ‘road’.
ATLAS quadrant in rz view
trigger chambersprecision chambers
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 12
THE L1 DECISIONDerived in the ‘Central Trigger Processor’ (CTP).
Multiplicitiesof objects above
pT thresholds
‘Conditions’:multiplicity
requirements
‘Items’: logicalcombinationsof ‘conditions’
L1 result as‘OR’ of all ‘items’
Inputs to HLT: L1 result and objects with pT,,.
CTP
calorimeter, muon
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 13
L1 SIMULATION: OVERVIEWMost developments originally for stand-alone applications.
Generation of MonteCarlo events for analysis purposes Rate/efficiency estimates Inputs for HLT tests Tests of L1 trigger hardware (~done for some compo- nents; just starting ‘slices’, configuration problem!)
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 14
THE HIGH-LEVEL TRIGGER (HLT)Good example for solid software process.
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 15
HLT: DESIGN OVERVIEW
EventFilter (EF)
ClassificationSelection~102 Hz
Hardware Implementation
LEVEL 2 (LVL2)~1 kHz
Level1 (L1)
~102 kHz
Read-OutSubsystemModules
High-Level Trigger: Design
HIGH-LEVEL TRIGGER (HLT)
Offline
Simplified subsystem view
Event- Filter
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 16
HLT: SELECTION SOFTWARE
HLTSSW
Steering Monitoring Service
1..*
MetaData Service
1..*ROBDataCollector
DataManager HLTAlgorithms
Processing Task
EventDataModel
LVL2PU Application
<<import>>
Offline EventDataModel
Offline Reconstruction
Algorithms
<<import>>
StoreGateAthena/Gaudi
<<import>><<import>>
InterfaceDependency
Package
EventFilter
Level2
PESA Core Software
PESA Algorithms
Offline Architecture & Core Software
Offline Reconstruction
Running in Level2 Processing Units (L2PU)+EF.
Set-up by HLT configuration
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 17
HLT DECISION (LEVEL2 AND EF)Overview of step-wise procedure with ‘dummy’ example Ze+e-
After every step: test + possibly rejection.
‘Physics Signature’: Ze+e- withpT>30 GeV
‘IntermediateSignature’
‘IntermediateSignature’
L1 result: 2 EM clusters
with pT>20 GeV
‘IntermediateSignature’
decision part algorithmic part
Teilchen 2, 4. November 2005 TSS: Triggering in ATLAS 18
AN ATLAS EVENT
H ZZ* e+e-+-
(mH = 130 GeV)
at high luminosity (1034 cm-2s-1)
The ‘hard’ Higgs event is overlaid with ~23‘minimum-bias’ and background events.
