Cms trigger system
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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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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

Physics Selection at LHC

  • Formidable task: Trigger Rejection 4.105

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


The cms trigger

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

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

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


Cms trigger system

Calorimeter Trigger Geometry


L1 electron photon trigger

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


L1 jet and triggers

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


Cms trigger system

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


Cms trigger system

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)


Cms trigger system

Calorimeter Trigger Primitives

1200 Synchronization and Link Boards: ECAL & HCAL Trigger Interface


Cms trigger system

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


Cms trigger system

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


Cms trigger system

Global Calorimeter Trigger

Processor Module

Input Module


Muons at lhc

L = 1034 cm-2s-1

|h| < 2.1

Muons at LHC

  • Issue is pT measurement of real muons


L1 muon trigger

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


Cms trigger system

L1 Muon Trigger Overview

|| < 1.2

0.8 < ||

|| < 2.4

|| < 2.1

Cavern: UXC55

Counting Room: USC55


Drift tube trigger track finder

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

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


Global muon trigger overview

Global Muon Trigger Overview


Cms trigger system

Muon Trigger Rates vs. Pt at 1034


Cms trigger system

Muon Trigger Efficiency vs. Pt


Cms trigger system

Drift Tube Track Finder

  • Phi Track-Finder

  • Eta Track Finder

  • DCC


Cms trigger system

Drift Tube Muon Sorter

  • Wedge Sorter

  • Barrel Sorter


Cms trigger system

CSC Trigger Full Chain

MPCCCB

Track-Finder Crate:

SP CCB MS

5 TMB

4 TMB

Fully Loaded Peripheral Crate


Cms trigger system

RPC Trigger Board


Cms trigger system

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)


L1 global trigger

L1 Global Trigger

  • Logic combinations of trigger objects sent by the Global Calorimeter Trigger and the Global Muon Trigger

  • Best 4 isolated electrons/photonsET, h, f

  • Best 4 non-isolated electrons/photonsET, h, f

  • Best 4 jets in forward regionsET, h, f

  • Best 4 jets in central regionET, h, f

  • Best 4 t-JetsET, h, f

  • Total ETSET

  • Total ET of all jets above thresholdHT

  • Missing ETETmissing, f(ETmissing)

  • 12 jet multiplicities Njets (different ET thresholds and h-regions)

  • Best 4 muonspT, 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 2x10 33

Level-1 Trigger table (2x1033)


Level 1 trigger table 10 34

Level-1 Trigger table (1034)


Cms trigger system

Global Trigger Crate

GTL_CONV

VME

interface

PSB

PSB

GTL6U


Cms trigger system

Trigger Control System Board


High level trigger

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 e t miss

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

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


Hlt summary 2x10 33 cm 2 s 1

HLT Summary: 2x1033 cm-2s-1


Hlt performance signal efficiency

HLT performance — signal efficiency

  • With previous selection cuts


Cms trigger system

DAQ and Filter Farm Preserie


Cms trigger system

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


Cms trigger system

  • Reserve


Drift tube local trigger

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

  • 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


Cms trigger system

RPC Trigger Algorithm

Pattern of hit strips is compared

to predefined patterns

corresponding to various pT

Implemented in FPGAs


Cms trigger system

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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