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 4.105 Bunch crossing rate 40MHz  permanent storage rate O(102)Hz

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!

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

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

Calorimeter Trigger Geometry    

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 E + H/E Electron/Photon 2-tower T E + H/E Isolated Electron/Photon Trigger threshold on sum of two towers 2x5-crystal strips>90% energy in 5x5 (Fine Grain) Neighbor EM + Had Quiet

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

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

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

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

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

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

Global Calorimeter Trigger Input Module Processor Module

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

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

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

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

CSC Muon Trigger Overview Muon Track-Finder Crate in underground counting room Muon Port Card Trig Motherboard Clock Control Board M P C D B T O N R L E Optical Link Peripheral Crate on iron disk Slow Control 1 of 5 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 quality tracks to Global L1 CSC CFEB ALCT 1 of 24 1 of 2 LVDB Anode Local Charged Track Board LV Distribution Board  Anode Front-end Board 

Global Muon Trigger Overview

Muon Trigger Rates vs. Pt at 1034 

Muon Trigger Efficiency vs. Pt

Drift Tube Track Finder Phi Track-Finder Eta Track Finder DCC

Drift Tube Muon Sorter Wedge Sorter Barrel Sorter

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

RPC Trigger Board

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

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/photons ET, 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 ET SET Total ET of all jets above threshold HT Missing ET ETmissing, 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

Level-1 Trigger table (2x1033) Threshold (GeV) Rate (kHz) Cumulative Rate (kHz) Isolated e/g 29 3.3 Di-e/g 17 1.3 4.3 Isolated muon 14 2.7 7.0 Di-muon 3 0.9 7.9 Single tau-jet 86 2.2 10.1 Di-tau-jet 59 1.0 10.9 1-jet, 3-jet, 4-jet 177, 86, 70 3.0 12.5 Jet*ETmiss 88*46 2.3 14.3 Electron*jet 21*45 0.8 15.1 Min-bias 16.0 TOTAL

Level-1 Trigger table (1034) Threshold (GeV) Rate (kHz) Cumulative Rate (kHz) Isolated e/g 34 6.5 Di-e/g 19 3.3 9.4 Isolated muon 20 6.2 15.6 Di-muon 5 1.7 17.3 Single tau-jet 101 5.3 22.6 Di-tau-jet 67 3.6 25.0 1-jet, 3-jet, 4-jet 250, 110, 95 3.0 26.7 Jet*ETmiss 113*70 4.5 30.4 Electron*jet 25*52 1.3 31.7 Muon*jet 15*40 0.8 32.5 Min-bias 1.0 33.5 TOTAL

VME interface PSB GTL6U GTL_CONV Global Trigger Crate

Trigger Control System Board

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

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)

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

HLT Summary: 2x1033 cm-2s-1 TOTAL Trigger Threshold (GeV) Rate (Hz) Cuml. rate (Hz) Inclusive electron 29 33 Di-electron 17 1 34 Inclusive photon 80 4 38 Di-photon 40, 25 5 43 Inclusive muon 19 25 68 Di-muon 7 72 Inclusive tau-jet 86 3 75 Di-tau-jet 59 76 1-jet * ETmiss 180 * 123 81 1-jet OR 3-jet OR 4-jet 657, 247, 113 9 89 Electron * jet 19 * 45 2 90 Inclusive b-jet 237 95 Calibration etc 10 105 TOTAL

HLT performance — signal efficiency With previous selection cuts Channel Efficiency (for fiducial objects) H(115 GeV)gg 77% H(160 GeV)WW* 2m 92% H(150 GeV)ZZ4m 98% A/H(200 GeV)2t 45% SUSY (~0.5 TeV sparticles) ~60% With RP-violation ~20% Wen 67% (fid: 60%) Wmn 69% (fid: 50%) Topm X 72%

DAQ and Filter Farm Preserie

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

Reserve

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

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

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

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 + - .AND. E T to t Th re sh e/ .OR. > Particle condition for muons for Et miss for e/ 