TRIGGERING IN THE ATLAS EXPERIMENT Thomas Schörner-Sadenius UHH Teilchenphysik II 4. November 2005

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS2 PHYSICS AT THE LHC II Comparison of SM and ‘new physics’ processes Small cross- sections for ‘new physics’ processes Understanding of SM processes important Backgrounds for ‘discovery physics’: Wbb, ttbb, W/Z pairs… Calibration, energy scale: Z  e + e -,  +  -, J/   e + e -,  +  -, W  jj… At high luminosity ~23 events overlaid … for cm -2 s -1 usually only one event … and small branching ratios (e.g. H   ). SM processes dominate. Necessity of efficient trigger!

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.

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS4 THE ATLAS EXPERIMENT - Length ~40 m - Diameter ~25 m - Weight ~7000 t 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 2005TSS: Triggering in ATLAS5 THE ‘INNER DETECTOR’ Pixel Detector: - 3 barrel layers - 24 end-discs channels -  R  =12  m,  z,R =~70  m - |  | <2.5 Silicon Tracker: - 4 barrel layers, |  | < end-discs, 1.4 <  < Area 60 m channels -  R  =16  m,  z,R =580  m Transition Radiation Tracker channels -  =170  m per straw - |  | <2.5

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS6 THE CALORIMETERS Hadronic Tile: scintillating tiles PMTs - Granularity  : <1.0, ( ) - L=11.4 m, R out =4.2 m Hadronic LAr Endcaps: - steel absorbers channels / EM LAr Accordeon: - lead absorbers channels  : <2.5, <3.2 Forward LAr: rods of 1mm - cell size 2-5cm 2 (4 rods) -  : <3.1, < copper, 2 tungsten LAr Pre-Sampler Against effects of energy losses in front of calorimeters

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS7 THE MUON SYSTEM Monitored Drift Tubes - 3 cylinders at R=7, 7.5, 10m - 3 layers at z=7, 10, 14 m tubes, cm -  space =80  m,  t =300ps (24-bit FADCs) Cathode Strip Chambers wires - only for |  |>2 in first layer -  space =60  m,  t =7ns Thin Gap Chambers channels - ~MWPCs Resistive Plate Chambers channels -  space =1cm - trigger signals in 1ns

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS8 THE ATLAS TRIGGER: OVERVIEW Multi-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 - 2  s latency (pipelines) } L2 - ‘Regions-of-Interest’ - ‘Fast rejection’ - Spec. algorithms - Latency ~10ms

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS9 THE LEVEL1-TRIGGER Selection based on high-p T objects from calo and muon. Multiplicities Regions- of- Interest Event decision for L1 Interface to front-end Muon candidates above p T thresholds Interface to higher trigger levels/DAQ: objects with p T, ,  Candidates for electrons/photons, taus/hadrons,jets above p T thres- holds. Energy sums above thresholds

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS10 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 E T ). 8 (4) (forward) jet E T thresholds. Total/missing E T from jets (sum of 0.2·0.2 jet elements to  ·  =0.4·0.2, conversion to E x,E y, then summation). Maximum of EM+HA E T in 2·2 ‘RoI’, isolation criteria (alternative core definitions?). Multiplicities for 8(8) e/  (  / hadron) E T thresholds. Builds candidate objects (RoIs): electrons/photons, taus/hadrons, jets. Ideas about core definitions, isolation criteria not really finalised.

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS11 THE MUON TRIGGER ‘Roads’ can be defined for 6 different p T thresholds (for which multiplicity counts are delivered to the CTP).  BCID =1.5 ns. Trigger chambers: 3 RPC stations for |  |< TGC stations for 1.05<|  |< ,  layers per station (TGC 2/3) p T information from hit coincidences in successive detector layers. Procedure: Put predefined ‘roads’ through all stations (width in  ~ p T ). If hit coincidences in 2(3) stations  muon candidate for p T thres- hold corresponding to ‘road’. ATLAS quadrant in rz view trigger chambers precision chambers

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS12 THE L1 DECISION Derived in the ‘Central Trigger Processor’ (CTP). Multiplicities of objects above p T thresholds ‘Conditions’: multiplicity requirements ‘Items’: logical combinations of ‘conditions’ L1 result as ‘OR’ of all ‘items’ Inputs to HLT: L1 result and objects with p T, , . CTP calorimeter, muon

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS13 L1 SIMULATION: OVERVIEW Most 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 2005TSS: Triggering in ATLAS14 THE HIGH-LEVEL TRIGGER (HLT) Good example for solid software process.

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS15 HLT: DESIGN OVERVIEW EventFilter (EF) Classification Selection ~10 2 Hz Hardware Implementation LEVEL 2 (LVL2) ~1 kHz Level1 (L1) ~10 2 kHz Read-Out Subsystem Modules High-Level Trigger: Design HIGH-LEVEL TRIGGER (HLT) Offline Simplified subsystem view Event- Filter

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS16 HLT: SELECTION SOFTWARE 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 2005TSS: Triggering in ATLAS17 HLT DECISION (LEVEL2 AND EF) Overview of step-wise procedure with ‘dummy’ example Z  e + e - After every step: test + possibly rejection. ‘Physics Signature’: Z  e + e - with p T >30 GeV ‘Intermediate Signature’ L1 result: 2 EM clusters with p T >20 GeV ‘Intermediate Signature’ decision partalgorithmic part

Teilchen 2, 4. November 2005TSS: Triggering in ATLAS18 AN ATLAS EVENT H  ZZ*  e + e -  +  - (m H = 130 GeV) at high luminosity (10 34 cm -2 s -1 ) The ‘hard’ Higgs event is overlaid with ~23 ‘minimum-bias’ and background events.