1 J. Varela, CMS Trigger, HEP2005, Lisbon, July 05 CMS Trigger System J. Varela LIP/IST-Lisbon &...

1J. Varela, CMS Trigger, HEP2005, Lisbon, July 05

CMS Trigger SystemCMS 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 LHCPhysics Selection at LHC

LEVEL-1 TriggerHardwired processors (ASIC, FPGA) Pipelined massive parallel

HIGH LEVEL Triggers Farms of

processors

10-9 10-6 10-3 10-0 103

25ns 3µs hour yearms

Reconstruction&ANALYSISTIER0/1/2

Centers

ON-lineOFF-line

sec

Giga Tera Petabit

Formidable task: Trigger Rejection 4.105

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


The CMS TriggerThe CMS Trigger

One of the more complex electronics systems ever built!

Level 1 Trigger: Hardwired processorsHigh Level Triggers: Farm of processors

Level-1 Trigger Requirements:Output: 100 kHz (50 kHz for initial

running)

Latency: 3 sec for collection, decision, propagation

HLT designed to output O(102)Hz


Level-1 TriggerLevel-1 TriggerInformation 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

HFHF HCALHCAL ECALECAL RPCRPC CSCCSC DTDT

PatternPatternComparatorComparator

Trigger Trigger

RegionalRegionalCalorimeterCalorimeter

TriggerTrigger

4 4 4 4 4+4 4+4

4 4 (with MIP/ISO bits)(with MIP/ISO bits)

MIP+MIP+ISO bitsISO bits

e, J, Ee, J, ETT, H, HTT, E, ETTmissmiss

Calorimeter TriggerCalorimeter Trigger Muon TriggerMuon Trigger

max. 100 kHz L1 Accept

Global TriggerGlobal Trigger

Global Muon TriggerGlobal Muon Trigger

GlobalGlobalCalorimeterCalorimeter

TriggerTrigger

Local Local DT TriggerDT Trigger

Local Local CSC TriggerCSC Trigger

DT TrackDT TrackFinderFinder

CSC TrackCSC TrackFinderFinder

40

MH

z p

ipe

line

, la

tenc

y <

3.2

s


Calorimeter Trigger Geometry


L1 Electron/Photon TriggerL1 Electron/Photon Trigger

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

Trigger threshold on sum of two towers

Electron/Photon2-tower T

E + H/E

Isolated Electron/Photon2x5-crystal strips>90%energy in 5x5 (Fine Grain)Neighbor EM + Had Quiet

E + H/E

Issue is rejection of huge jet background


L1 Jet and L1 Jet and Triggers Triggers

Single, double, triple and quad thresholds possible

Possible also to cut on jet multiplicities

Also ETmiss, ET and ET(jets) triggers

Sliding window:- granularity is 4x4 towers = trigger region- jet ET summed in 3x3 regions , = 1.04

“-like” shapes identified for trigger

Issues are jet energy resolution and tau identification


Calorimeter Trigger Rates at 10Calorimeter Trigger Rates at 103434

Rates drop sharply with trigger Et cutoff

Provides ability to tune cuts to sustain rates during operationSeveral cuts are available to optimize efficiency versus rateQCD background rates are within target


Calibrated Hadron Level Jet Et (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 Efficiency

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300MC -jet ET

Efficiency

>95% at Pt =180 GeV

for (incl. minbias) for a 1 kHz rate

efficy

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200 250 300

Efficiency

QCDCMSIM 116 ORCA 4.2.0

(With minimum bias)L = 1034 cm-2 s-11-Jet Et 250 GeV

286.5

2-Jet Et 200 GeV

232.5

3-Jet Et 100 GeV

157.5

4-Jet Et 80 GeV

106.5

QCD jet efficiency for | |<5

0

0.2

0.4

0.6

0.8

1

0 10 20 30 40 50 60 70 80 90 100MC e/ ET

Efficiency

>95% at PT =35 GeV

for e in top events(incl. minbias) For a 7kHz rate

e/ efficy


Calorimeter Trigger PrimitivesCalorimeter Trigger Primitives1200 Synchronization and Link Boards: ECAL & HCAL Trigger Interface


SORTASICs(w/heat sinks)

EISO

EISO

Bar Code

Input

DC-DCConverters

Clock delay adjust

Clock Input

Oscillator

DC-DC

Adder

mezzlink

cards

BSCANASICs

PHASEASICs

MLUs

BackBar Code

Front

Regional Calorimeter Trigger Regional Calorimeter Trigger Receiver Card: Electron Isolation & Clock: Jet/Summary:

ReceiverMezz. Card

BSCANASICs

SortASICs

BSCANASICs

PhaseASIC

EISO

Clock

Front

Back


Full Regional Cal. Trigger CrateFull Regional Cal. Trigger Crate

18 Such Crates make up the full RCT System covering ||<5 & 0 < < 2.

Rear: Receiver Cards Front: Electron, Jet, Clock Cards


Global Calorimeter Trigger Global Calorimeter Trigger

Input Module Processor Module


Muons at LHCMuons at LHC

Issue is pT measurement of real muons

threshold [GeV/c]T

p01 02 03 04 05 06 07 08 0

10-2

10-1

1

10

102

103

104

105

106

±/±K

L0K

c

b

*/0Z±

L = 1034 cm-2s-1

< 2.1


L1 Muon triggerL1 Muon triggerLevel-1 -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 OverviewL1 Muon Trigger Overview

|| < 1.2 || < 2.40.8 < || || < 2.1

Ca

vern

: UX

C5

5C

ou

ntin

g R

oom

: US

C55


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

Phi Track Finder(Sector Processor)

Drift Tube Trigger Track FinderDrift Tube Trigger Track Finder


CSC Muon Trigger OverviewCSC Muon Trigger Overview

CSC

CFEBCFEBCFEB CFEB

ALCT1 of 24

CFEB

1 of 2

LVDB

LV Distribution Board

1 of 5

1 of 5

AnodeFront-end

Board

Cathode Front-end

Board

Anode LocalCharged Track

Board

MPC

DMB

TMB

DMB

TMB

DMB

TMB

DMB

TMB

DMB

TMB

DMB

TMB

DMB

TMB

DMB

TMB

DMB

TMB

CCBC

ONTROLLER

Peripheral Crate

on iron diskSlow Control

Muon Track-Finder Crate in underground

counting room

Trig MotherboardMuon Port Card

Clock Control Board

OpticalLink

•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


Global Muon Trigger OverviewGlobal Muon Trigger Overview


Muon Trigger Rates vs. PMuon Trigger Rates vs. Pt t at 10at 103434


Muon Trigger Efficiency vs. PMuon Trigger Efficiency vs. Ptt


Drift Tube Track Finder Drift Tube Track Finder

Phi Track-Finder

Eta Track Finder

DCC


Drift Tube Muon SorterDrift Tube Muon Sorter

Wedge Sorter

Barrel Sorter


CSC Trigger Full ChainCSC Trigger Full Chain

4 TMB4 TMB5 TMB5 TMB

Track-Finder Crate:Track-Finder Crate:SPSP CCB CCB MSMS

MPCMPCCCBCCB

Fully Loaded Peripheral CrateFully Loaded Peripheral Crate


RPC Trigger BoardRPC Trigger Board


Global Muon Trigger Logic BoardGlobal Muon Trigger Logic Board

Input board (4x4 Input board (4x4 )) Logic BoardLogic Board

Logicfwd

Logicbrl

ROPMIP/ISOfwd

MIP/ISObrl

Sort

4 SCSI 4 SCSI connectors connectors on Logic on Logic BoardBoard

3x4 on input 3x4 on input boardboard


L1 Global TriggerL1 Global Trigger Logic combinations of trigger objects sent by the Global Calorimeter Trigger and the Global Muon Trigger Best 4 isolated electrons/photons ET, , Best 4 non-isolated electrons/photons ET, , Best 4 jets in forward regions ET, , Best 4 jets in central region ET, , Best 4 -Jets ET, , Total ET ET

Total ET of all jets above threshold HT

Missing ET ETmissing, (ET

missing) 12 jet multiplicities Njets (different ET thresholds and -regions) Best 4 muons pT, charge, , , 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 (2x10Level-1 Trigger table (2x103333))

Trigger Threshold

(GeV)

Rate (kHz) Cumulative Rate (kHz)

Isolated e/ 29 3.3 3.3

Di-e/ 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 0.9 16.0

TOTAL 16.0


Level-1 Trigger table (10Level-1 Trigger table (103434))

Trigger Threshold

(GeV)

Rate (kHz) Cumulative Rate (kHz)

Isolated e/ 34 6.5 6.5

Di-e/ 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 33.5


VMEinterface PSBPSB

GTL6U

GTL_CONV

Global Trigger CrateGlobal Trigger Crate


Trigger Control System BoardTrigger Control System Board


High-Level TriggerHigh-Level TriggerRuns 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: HLT selection: , , , jets and E, jets and ETTmissmiss

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 photonsHLT selection: electrons and photons

Level-2

Level-3

Level-1

Level-2.5

PhotonsThreshold cut

Isolation

ElectronsTrack reconstruction

E/p, matching () cut

ECAL reconstructionThreshold cut

Pixel matching

• 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


HLT Summary: 2x10HLT Summary: 2x103333 cm cm-2-2ss-1-1

Trigger Threshold(GeV)

Rate (Hz) Cuml. rate (Hz)

Inclusive electron 29 33 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 4 72

Inclusive tau-jet 86 3 75

Di-tau-jet 59 1 76

1-jet * ETmiss 180 * 123 5 81

1-jet OR 3-jet OR 4-jet

657, 247, 113 9 89

Electron * jet 19 * 45 2 90

Inclusive b-jet 237 5 95

Calibration etc 10 105

TOTAL 105


HLT performance HLT performance — signal efficiency— signal efficiencyWith previous selection cuts

Channel Efficiency

(for fiducial objects)

H(115 GeV) 77%H(160 GeV)WW* 2 92%H(150 GeV)ZZ4 98%A/H(200 GeV)2 45%SUSY (~0.5 TeV sparticles) ~60%

With RP-violation ~20%

We 67% (fid: 60%)

W 69% (fid: 50%)

TopX 72%


DAQ and Filter Farm PreserieDAQ and Filter Farm Preserie


SummarySummary

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


Synchronous pipelined system (40 MHz)

trigger boards TRB

server board SB

to Sector Collector

8 cm

16 cm

2 metres

Drift Tube local-trigger


Global Muon Trigger Efficiencies

DTCSCRPCGMT smart

GMT ORGMT ANDGMT smart

Muon Trigger Efficiency

GMT Efficiency

Optimal combinationOptimal combinationhigh efficiency, small ratehigh efficiency, small rate

2.087.4AND

2.997.3SMART

5.498.1OR

Rate

kHz

for 14

GeV

21GMT

Option

Rates for L=2x1033 cm-2s-1


RPC Trigger AlgorithmRPC Trigger Algorithm

Pattern of hit strips is comparedto predefined patternscorresponding to various pT

Implemented in FPGAs


Example:Two leptons back-to-back in , opposite charge, with missing Et above threshold

An algorithm is a logical combination of trigger objects satisfying defined threshold, topology and quality criteria

There are 128 algorithms running in parallel.

Global Trigger AlgorithmsGlobal Trigger Algorithms

+

-

.AND. ET

tot ET

Th resh

e/

e/

.OR. .AND. ET

tot ET

Th resh>

Particle condition for muons

Particle conditionfor Et miss

Particle conditionfor Et miss

Particle condition for e/

>

1 J. Varela, CMS Trigger, HEP2005, Lisbon, July 05 CMS Trigger System J. Varela LIP/IST-Lisbon &...

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