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CMS Trigger System

CMS Trigger System. J. Varela LIP/IST-Lisbon & CERN on behalf of the CMS collaboration HEP2005 International Europhysics Conference on High Energy Physics July 21st-27th 2005, Lisboa, Portugal. Physics Selection at LHC. Formidable task: Trigger Rejection 4.10 5

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CMS Trigger System

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  1. CMS Trigger System J. Varela LIP/IST-Lisbon & CERN on behalf of the CMS collaboration HEP2005 International Europhysics Conference on High Energy Physics July 21st-27th 2005, Lisboa, Portugal

  2. Physics Selection at LHC • Formidable task: Trigger Rejection 4.105 • Bunch crossing rate 40MHz  permanent storage rate O(102)Hz

  3. The CMS Trigger Level 1 Trigger: Hardwired processors High Level Triggers: Farm of processors • Level-1 Trigger Requirements: • Output: 100 kHz (50 kHz for initial running) • Latency: 3 msec for collection, decision, propagation • HLT designed to output O(102)Hz One of the more complex electronics systems ever built!

  4. Level-1 Trigger • Information from Calorimeters and Muon detectors • Electron/photon triggers • Jet and missing ET triggers • Muon triggers • Backgrounds are huge • Sophisticated trigger algorithms • Steep functions of thresholds • Synchronous and pipelined • Bunch crossing time = 25 ns • Time needed for decision (+its propagation) ≈ 3 s • Highly complex • Trigger primitives: ~5000 electronics boards of 7 types • Regional/Global: 45 crates, 630 boards, 32 board types • Large flexibility • Large number of electronics programmable parameters • Most algorithms implemented in re-programmable FPGAs

  5. Muon Trigger Calorimeter Trigger RPC CSC DT HF HCAL ECAL Local CSC Trigger Local DT Trigger RegionalCalorimeterTrigger PatternComparator Trigger CSC TrackFinder DT TrackFinder GlobalCalorimeterTrigger 40 MHz pipeline, latency < 3.2 ms 4+4 m 4 m 4 m MIP+ISO bits Global Muon Trigger e, J, ET, HT, ETmiss 4 m (with MIP/ISO bits) Global Trigger max. 100 kHz L1 Accept Level-1 Trigger Dataflow

  6.    Calorimeter Trigger Geometry  

  7. 2-tower E E + H/E + H/E T L1 Electron/Photon Trigger Issue is rejection of huge jet background • Electromagnetic trigger based on 3x3 trigger towers • Each tower is 5x5 crystals in ECAL (barrel; varies in end-cap) • Each tower is single readout tower in HCAL Electron/Photon Isolated Electron/Photon Trigger threshold on sum of two towers 2x5-crystal strips>90% energy in 5x5 (Fine Grain) Neighbor EM + Had Quiet

  8. L1 Jet and  Triggers Issues are jet energy resolution and tau identification • Single, double, triple and quad thresholds possible • Possible also to cut on jet multiplicities • Also ETmiss, SET and SET(jets) triggers • Sliding window: • granularity is 4x4 towers = trigger region • jet ET summed in 3x3 regions , = 1.04 “-like” shapes identified for  trigger

  9. Calorimeter Trigger Rates at 1034 Rates drop sharply with trigger Et cutoff Provides ability to tune cuts to sustain rates during operation Several cuts are available to optimize efficiency versus rate QCD background rates are within target

  10. Efficiency Efficiency e/ efficy QCD jet efficiency for | |<5 1 1 0.8 >95% at PT =35 GeV 0.6 0.8 for e in top events (incl. minbias) For a 7kHz rate 0.4 0.6 0.2 QCD 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 CMSIM 116 ORCA 4.2.0 MC e/ ET (With minimum bias) 0.4 34 -2 -1 L = 10 cm s Efficiency 1-Jet E 250 GeV t  efficy 2-Jet E 200 GeV 1 t 3-Jet E 100 GeV 0.2 t 4-Jet E 80 GeV 0.8 t >95% at Pt =180 GeV 106.5 157.5 232.5 286.5 0.6 0 for  (incl. minbias) for a 1 kHz rate 0 5 0 100 150 200 250 300 0.4 Calibrated Hadron Level Jet E (GeV) t 0.2 0 0 5 0 100 150 200 250 300 MC -jet ET Calorimeter Trigger Efficiency >95% at PT =286, 232, 157, 106 GeV for individual 1,2,3,4 jet triggers (incl. minbias) (~0.5 kHz rate each totaling ~2 kHz)

  11. Calorimeter Trigger Primitives 1200 Synchronization and Link Boards: ECAL & HCAL Trigger Interface

  12. Regional Calorimeter Trigger • Receiver Card: Electron Isolation & Clock: Jet/Summary: Receiver Mezz. Card Bar Code Front Adder EISO mezz link cards Front EISO SORT ASICs (w/heat sinks) Input BSCAN ASICs EISO DC-DC Back Oscillator Bar Code Clock Phase ASIC PHASE ASICs Clock Input Back Clock delay adjust BSCAN ASICs MLUs DC-DC Converters BSCAN ASICs Sort ASICs

  13. Full Regional Cal. Trigger Crate • 18 Such Crates make up the full RCT System covering |h|<5 & 0 < f < 2p. Front: Electron, Jet, Clock Cards Rear: Receiver Cards

  14. Global Calorimeter Trigger Processor Module Input Module

  15. L = 1034 cm-2s-1 |h| < 2.1 Muons at LHC • Issue is pT measurement of real muons

  16. L1 Muon trigger • Level-1 m-trigger info from: • Dedicated trigger detector: RPCs (Resistive plate chambers) • Excellent time resolution • Muon chambers with accurate position resolution • Drift Tubes (DT) in barrel • Cathode Strip Chambers (CSC) in end-caps

  17. L1 Muon Trigger Overview || < 1.2 0.8 < || || < 2.4 || < 2.1 Cavern: UXC55 Counting Room: USC55

  18. Drift Tube Trigger Track Finder Phi Track Finder (Sector Processor) • Track Finder Processor • Pipeline logic running at 40MHz • (LHC bunch crossing frequency) • Implemented in programmable logic • devices • Based on extrapolation and pattern • matching methods Drift Tubes

  19. C C B D M B T M B D M B T M B D M B T M B D M B T M B D M B T M B M P C T M B D M B T M B D M B T M B D M B T M B D M B C O N T R O L L E R 1 of 5 1 of 5 CFEB CFEB CFEB CFEB CFEB 1 of 2 1 of 24 ALCT LVDB CSC   CSC Muon Trigger Overview Muon Track-Finder Crate in undergroundcounting room Muon Port Card Trig Motherboard Clock Control Board Optical Link Peripheral Crate on iron disk SlowControl Cathode Front-end Board • Start w/ wire & strip segment combinations: • Wires:25ns bunch xing • Strips: precision  • Form “Trigger Primitives” • Link into tracks • Assign pT, , and  • Send highest qualitytracks to Global L1 Anode LocalCharged TrackBoard LV Distribution Board Anode Front-end Board

  20. Global Muon Trigger Overview

  21.  Muon Trigger Rates vs. Pt at 1034

  22. Muon Trigger Efficiency vs. Pt

  23. Drift Tube Track Finder • Phi Track-Finder • Eta Track Finder • DCC

  24. Drift Tube Muon Sorter • Wedge Sorter • Barrel Sorter

  25. CSC Trigger Full Chain MPCCCB Track-Finder Crate: SP CCB MS 5 TMB 4 TMB Fully Loaded Peripheral Crate

  26. RPC Trigger Board

  27. Global Muon Trigger Logic Board 4 SCSI connectors on Logic Board 3x4 on input board MIP/ISO brl Logicfwd Sort Logicbrl MIP/ISO fwd ROP Logic Board Input board (4x4 m)

  28. L1 Global Trigger • Logic combinations of trigger objects sent by the Global Calorimeter Trigger and the Global Muon Trigger • Best 4 isolated electrons/photons ET, h, f • Best 4 non-isolated electrons/photonsET, h, f • Best 4 jets in forward regions ET, h, f • Best 4 jets in central region ET, h, f • Best 4 t-Jets ET, h, f • Total ETSET • Total ET of all jets above threshold HT • Missing ETETmissing, f(ETmissing) • 12 jet multiplicities Njets (different ET thresholds and h-regions) • Best 4 muons pT, charge, f, h, quality, MIP, isolation • Thresholds(pT, ET, NJets) • Optional topological and other conditions (geometry, isolation, charge, quality) • 128 algorithms running in parallel

  29. Level-1 Trigger table (2x1033)

  30. Level-1 Trigger table (1034)

  31. Global Trigger Crate GTL_CONV VME interface PSB PSB GTL6U

  32. Trigger Control System Board

  33. High-Level Trigger • Runs on large CPU farm • Code as close as possible to offline reconstruction • Selection must meet CMS physics goals • Output rate to permanent storage limited to O(102)Hz • Reconstruction on demand • Reject as soon as possible • Trigger “Levels”: • Level-2: use calorimeter and muon detectors • Level-2.5: also use tracker pixel detectors • Level-3: includes use of full information, including tracker • “Regional reconstruction”: e.g. tracks in a given road or region

  34. HLT selection: , , jets and ETmiss • Muons • Successive refinement of momentum measurement; + isolation • Level-2: reconstructed in muon system; must have valid extrapolation to collision vertex; + calorimeter isolation • Level-3: reconstructed in inner tracker; + tracker isolation • -leptons • Level-2: calorimetric reconstruction and isolation • Level-3: tracker isolation • Jets and Etmiss • Jet reconstruction with iterative cone algorithm • ETmiss reconstruction (vector sum of towers above threshold)

  35. Level-1 ECAL reconstruction Threshold cut Level-2 Level-2.5 Pixel matching Level-3 Electrons Track reconstruction E/p, matching (Dh) cut Photons Threshold cut Isolation HLT selection: electrons and photons • Issue is electron reconstruction and rejection • Higher ET threshold on photons • Electron reconstruction • key is recovery of radiated energy • Electron rejection • key tool is pixel detector

  36. HLT Summary: 2x1033 cm-2s-1

  37. HLT performance — signal efficiency • With previous selection cuts

  38. DAQ and Filter Farm Preserie

  39. Summary • The CMS Trigger System is close to become reality after a long period of simulation studies, hardware prototyping and system construction • The CMS trigger design meets the challenging LHC requirements: • Large rate reduction • High efficiency for signal events • Wide inclusive selection (open to the unexpected) • Huge flexibility allowing future adaptation to the unknown

  40. Reserve

  41. Drift Tube local-trigger trigger boards TRB server board SB to Sector Collector 8 cm Synchronous pipelined system (40 MHz) 16 cm 2 metres

  42. GMT Option • e%|h|<2.1 • Rate • kHz • for 14 GeV • OR • 98.1 • 5.4 • SMART • 97.3 • 2.9 • AND • 87.4 • 2.0 Rates for L=2x1033 cm-2s-1 Optimal combinationhigh efficiency, small rate Global Muon Trigger Efficiencies DT CSC RPC GMT smart Muon Trigger Efficiency GMT OR GMT AND GMT smart GMT Efficiency

  43. RPC Trigger Algorithm Pattern of hit strips is compared to predefined patterns corresponding to various pT Implemented in FPGAs

  44. Particle condition for muons Particle condition for Et miss Particle condition for e/ Particle condition for Et miss  + e/ > .AND. .AND. .OR. to t Th re sh to t Th re sh E E E E T T T T  - e/ > Global Trigger Algorithms • An algorithm is a logical combination of trigger objects satisfying defined threshold, topology and quality criteria • There are 128 algorithms running in parallel. • Example: • Two leptons back-to-back in , opposite charge, with missing Et above threshold

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