Triggering CMS - PowerPoint Presentation

Slide1

Triggering CMS

Wesley H. Smith

U. Wisconsin – Madison

CMS Trigger Coordinator

Seminar, Texas A&M

April 20, 2011

Outline:

Introduction to CMS

Trigger Challenges & Architecture

Level -1 Trigger Implementation & Performance

Higher Level Trigger Algorithms & Performance

The Future: SLHC TriggerSlide2

LHC Collisions

with every bunch crossing

23 Minimum Bias events

with ~1725 particles producedSlide3

LHC Physics & Event Rates

At design

L

= 10

34

cm

-2s-123 pp events/25 ns xing~ 1 GHz input rate“Good” events contain ~ 20 bkg. events1 kHz W events10 Hz top events< 104 detectable Higgs decays/yearCan store ~ 300 Hz eventsSelect in stagesLevel-1 Triggers1 GHz to 100 kHzHigh Level Triggers100 kHz to 300 HzSlide4

Collisions (p-p) at LHC

Event size: ~1 MByte Processing Power: ~X TFlop

All charged tracks with pt > 2 GeV

Reconstructed tracks with pt > 25 GeV

Operating conditions:

one “good” event (e.g Higgs in 4 muons )

+ ~20 minimum bias events)

Event rateSlide5

CMS Detector Design

MUON BARREL

CALORIMETERS

Pixels

Silicon

Microstrips

210 m

2

of silicon sensors

9.6M channels

ECAL

76k scintillating

PbWO4 crystals

Cathode Strip Chambers

(

CSC

)

Resistive Plate Chambers

(

RPC

)

Drift Tube

Chambers

(

DT

)

Resistive Plate

Chambers

(RPC)

Superconducting Coil,

4 Tesla

IRON YOKE

TRACKER

MUON

ENDCAPS

HCAL

Plastic scintillator/brass

sandwich

Today:

RPC |

η

| < 1.6 instead of 2.1 & 4th endcap layer missing

Level-1 Trigger Output

Today: 50 kHz

(instead of 100)Slide6

LHC Trigger & DAQ Challenges

Computing Services

16 Million channels

Charge

Time

Pattern

40 MHz

COLLISION RATE

100 - 50 kHz

1 MB

EVENT DATA

1 Terabit/s

READOUT

50,000 data

channels

200 GB buffers

~ 400 Readout

memories

3 Gigacell buffers

500 Gigabit/s

5 TeraIPS

~ 400 CPU farms

Gigabit/s

SERVICE LAN

Petabyte ARCHIVE

Energy

Tracks

300 Hz

FILTERED

EVENT

EVENT BUILDER.

A large switching network (400+400 ports) with total throughput ~ 400Gbit/s forms the interconnection between the sources (deep buffers) and the destinations (buffers before farm CPUs).

EVENT FILTER.

A set of high performance commercial processors organized into many farms convenient for on-line and off-line applications.

SWITCH NETWORK

LEVEL-1

TRIGGER

DETECTOR CHANNELS

Challenges:

1 GHz of Input Interactions

Beam-crossing every 25 ns with ~ 23 interactions produces over 1 MB of data

Archival Storage at about 300 Hz of 1 MB eventsSlide7

Level 1 Trigger OperationSlide8

CMS Trigger LevelsSlide9

L1 Trigger Locations

Underground Counting Room

Central rows of racks for

trigger

Connections via high-speed copper links to adjacent rows of ECAL & HCAL readout racks with trigger primitive circuitry

Connections via optical

fiber to muon trigger primitive generatorson the detectorOptical fibersconnected via“tunnels” to detector(~90m fiber lengths)Rows of Racks containing trigger & readout electronics

7m thick

shielding

wall

USC55Slide10

CMS Level-1 Trigger & DAQ

Overall Trigger & DAQ Architecture: 2 Levels:

Level-1 Trigger:

25 ns input

3.2

μs latency

Interaction rate: 1 GHzBunch Crossing rate: 40 MHzLevel 1 Output: 100 kHz (50 initial)Output to Storage: 100 HzAverage Event Size: 1 MBData production 1 TB/day

UXC





USCSlide11

CMS Calorimeter Geometry

EB, EE, HB, HE map to 18 RCT crates

Provide e/

γ

and jet,

τ,

ET triggers1 trigger tower (.087η✕

.087

φ

) = 5

✕

5 ECAL xtals = 1 HCAL tower

2 HF calorimeters map on to 18 RCT crates

Trigger towers:

Δη

=

Δ

ϕ

= 0.087Slide12

ECAL Endcap Geometry

Map non-projective x-y trigger crystal geometry onto projective trigger towers:

Individual

crystal

5 x 5 ECAL xtals

≠

1 HCAL tower in detail+ZEndcap

-Z

EndcapSlide13

Calorimeter Trig. Processing

Trigger Tower

25 Xtals (TT)

TCC

(LLR)

CCS

(CERN)

SRP

(CEA

DAPNIA)

DCC

(LIP)

TCS

TTC

Trigger primitives @800 Mbits/s

OD

DA

Q

@100 kHz

L1

Global TRIGGER

Regional

CaloTRIGGER

Trigger Tower Flags (TTF)

Selective Readout Flags (SRF)

SLB

(LIP)

Data path

@100KHz (Xtal Datas)

T

rigger

C

oncentrator

C

ard

S

ynchronisation &

L

ink

B

oard

C

lock &

C

ontrol

S

ystem

S

elective

R

eadout

P

rocessor

D

ata

C

oncentrator

C

ard

T

iming,

T

rigger &

C

ontrol

T

rigger

C

ontrol

S

ystem

Level 1 Trigger (L1A)

From : R. Alemany LIPSlide14

Calorimeter Trig.Overview

(located in underground counting room)

Calorimeter

Electronics

Interface

Regional

Calorimeter

Trigger

Receiver

Electron Isolation

Jet/Summary

Global Cal. Trigger

Sorting,

E

T

Miss

, ΣE

T

Global

Trigger

Processor

Global Muon Trigger

Iso

Mu

MinIon

Tag

Lumi

-

nosity Info.

4K 1.2

Gbaud serial links w

/2 x

(8 bits E/H/FCAL Energy+ fine grain structure bit) + 5 bits error detection code

per 25 ns crossing

US CMS HCAL:BU/FNAL/

Maryland/Princeton

CMS ECAL:

Lisbon/Palaiseau

US CMS:

Wisconsin

Bristol/CERN/Imperial/LANL

CMS:

Vienna

72 φ

✕ 60 η

H/ECALTowers (.087φ ✕.087η

for η < 2.2 & .174-.195

η,

η>2.2)HF: 2

✕

(12

φ

✕

12

η

)

Copper 80 MHz Parallel

4 Highest E

T

:

Isolated & non-

isol

.

e/

γ

Central, forward,

τ

jets,

E

x

,

E

y

from each crate

MinIon

& Quiet

Tags for

each 4

φ

✕

4

η

region

GCT Matrix

μ

+ Q bits

IC/

LANL

/UWSlide15

ECAL Trigger Primitives

Test beam results (45 MeV per xtal):Slide16

CMS Electron/Photon AlgorithmSlide17

CMS

τ

/ Jet AlgorithmSlide18

L1 Cal. Trigger Synchronization

BX ID Efficiency –

e/

γ

& Jets

Sample of min bias events, triggered by BSC coincidence, with good vertex and no scrapingFraction of candidates that are in time with bunch-crossing (BPTX) trigger as function of L1 assigned ETAnomalous signals from ECAL, HF removedNoise pollutes BX ID efficiency at low E

T

values

e/

γ

Jet/

τ

Forward Jet Slide19

L1 efficiency for electrons

Sample of ECAL Activity HLT triggers (seeded by L1

ZeroBias

)

Anomalous ECAL signals removed using standard cuts

EG trigger efficiency for electrons from conversions

Standard loose electron isolation & IDConversion ID (inverse of conversion rejection cuts) to select electron-like objectsEfficiency shown w.r.t ET of the electron supercluster, for L1 threshold of 5 GeV (top), 8 GeV (bottom)Two η ranges shown: Barrel (black), endcaps (red)L1_EG5

L1

_

EG8

With RCT CorrectionSlide20

Jet Trigger Efficiency

minimum-bias trigger

jet energy correction: online / offline match

turn-on curves steeperSlide21

Reduced RE system

|

η

| < 1.6

1.6

ME4/1

MB1

MB2

MB3

MB4

ME1

ME2

ME3

*Double Layer

*RPC

Single Layer

CMS Muon ChambersSlide22

Muon Trigger Overview

|

η| < 1.2

|

η| < 2.4

0.8 <

|η| |η| < 2.1|η| < 1.6 in 2009

Cavern: UXC55

Counting Room: USC55Slide23

CMS Muon Trigger Primitives

Memory to store patterns

Fast logic for matching

FPGAs are idealSlide24

CMS Muon Trigger

Track Finders

Memory to store patterns

Fast logic for matching

FPGAs are ideal

Sort based on P

T, Quality - keep loc.Combine at next level - matchSort again - Isolate?Top 4 highest PT and quality muons with location coord.Match with RPC Improve efficiency and qualitySlide25

DT

L1 Muon Trigger Synchronization

BX ID Efficiency – CSC, DT, RPC

All muon trigger timing within ± 2 ns, most better & being improved

RPC

CSC



Log

PlotSlide26

L1 Muon Efficiency vs. p

T

01/04/2011

Barrel

EndCap

OverLap

L1_Mu7

L1_Mu10

L1_Mu12

L1_Mu20Slide27

CMS Global TriggerSlide28

Global L1 Trigger AlgorithmsSlide29

“Δelta” or “correlation” conditions

Unique Topological Capability of CMS L1 Trigger

separate objects in

η

&

Φ

:Δ ≥ 2 hardware indicesϕ: Δ ≥ 20 .. 40 degreesPresent Use:eγ / jet separation to avoid triggering twice on the same object in a correlation triggerobjects to be separated by one empty sector (20 degrees)Slide30

High Level Trigger StrategySlide31

All processing beyond Level-1 performed in the Filter Farm

Partial event reconstruction “on demand” using full detector resolution

High-Level Trig. Implementation

8 “slices”Slide32

Start with L1 Trigger Objects

Electrons, Photons,

τ

-jets, Jets, Missing E

T

, Muons

HLT refines L1 objects (no volunteers)GoalKeep L1T thresholds for electro-weak symmetry breaking physicsHowever, reduce the dominant QCD backgroundFrom 100 kHz down to 100 Hz nominallyQCD background reductionFake reduction: e±, γ, τImproved resolution and isolation: μExploit event topology: JetsAssociation with other objects: Missing ETSophisticated algorithms necessary

Full reconstruction of the objects

Due to time constraints we avoid full reconstruction of the event - L1 seeded reconstruction of the objects only

Full reconstruction only for the HLT passed eventsSlide33

Electron & Photon HLT

“Level-2” electron:

Search for match to Level-1 trigger

1-tower margin around 4x4-tower trig. region

Bremsstrahlung

recovery “super-clustering”

Road along φ — in narrow η-window around seedCollect all sub-clusters in road η “super-cluster”Select highest ET clusterCalorimetric (ECAL+HCAL) isolation“Level-3” PhotonsTight track isolation“Level-3” Electrons

Electron track reconstruction

Spatial matching of ECAL cluster

and pixel track

Loose track isolation in

a “hollow” cone

basic cluster

super-clusterSlide34

“Tag & probe” HLT Electron Efficiency

Use Z mass resonance to select electron pairs & probe efficiency of selection

Tag: lepton passing very tight selection with very low fake rate (<<1%)

Probe: lepton passing softer selection & pairing with Tag object such that invariant mass of tag & probe combination is consistent with Z resonance

Efficiency =

Npass/Nall

Npass → number of probes passing the selection criteriaNall → total number of probes counted using the resonanceBarrelEndcapThe efficiency of electron trigger paths in2010 data reaches 100% within errorsElectron (ET Thresh>17 GeV) with Tighter Calorimeter-basedElectron ID+Isolation

at HLTSlide35

Muon HLT & L1 Efficiency

Both isolated & non-isolated muon trigger shown

Efficiency loss is at Level-1, mostly at high-

η

Improvement over these curves already done

Optimization of DT/CSC overlap & high-

η regionsSlide36

Jet HLT Efficiency

Jet efficiencies calculated

Relative to a lower threshold trigger

Relative to an independent trigger

Jet efficiencies plotted vs. corrected offline

reco

Anti-kT jet energyPlots are from 2011 run 161312HLT_Jet370BarrelEndcap AllHLT_Jet240BarrelEndcap AllSlide37

Summary of Current Physics Menu(5E32) by Primary Dataset

Jet

Single Jet,

DiJetAve,MultiJet

QuadJet

, ForwardJets, Jets+TausHT Misc. hadronic SUSY triggersMETBtagMET triggers, Btag POG triggersSingleMuSingle mu triggers (no had. requirement)DoubleMuDouble mu trigger (no had. requirement)SingleElectronSingle e triggers (no had. requirement)DoubleElectronDouble e triggers (no had requirement)PhotonPhotons (no had. requirement)MuEGMu+photon or ele (no had. requirement)ElectronHad

electrons +

had.

activity

PhotonHad

Photons +

had.

activity

MuHad

Muons +

had.

activity

Tau

Single and Double taus

TauPlusX

X-triggers with taus

MuOniaJ/psi, upsilon

+

Commisioning,

Cosmics, MinimumBias

Expected rate of each PD is

15-30 Hz @ 5E32

Writing a total of O(360) Hz. (Baseline is 300 Hz)Slide38

Trigger Rates in 2011

Trigger rate predictions based mostly on data.

Emulation of paths via

OpenHLT

working well for most of trigger table

Data collected already

w/ sizeable PU (L=2.5E32 → PU~7)Allows linear extrapolation to higher luminosity scenariosEmulated &Online Rates: Agreement to ≲ 30%, data-only check of measured ratevs. separate emulation Slide39

Approx. evolution for some triggers

L=5E32

Single

Iso

Mu ET: 17 GeV

Single

Iso elec ET: 27 GeVDouble Mu ET: 6, 6 GeVDouble Elec ET: 17, 8 GeVe+mu ET: 17,8 & 8,17 GeVDi-photon: 26, 18 GeVe/mu + tau: 15, 20 GeVHT: 440 GeVHT+MHT: 520 GeVL=2E33Single Iso Mu ET: 30 GeVSingle Iso elec ET: 50 GeVDouble Mu ET: 10,10 GeVDouble Elec ET: 17, 8 GeV*e+mu ET: 17,8 & 8,17 GeV*Di-photon: 26, 18 GeV*e/mu + tau: 20, 20-25 GeVHT:HT+MHT:Targeted rate of each line is ~10-15 Hz.Overall menu has many cross triggers for signal and prescaled triggers for efficiencies and fake rate measurements as well* Tighter ID and

Iso

conditions, still rate and/or efficiency concerns

Possibly large

uncertainty

due

to pile-upSlide40

HLT at 1E33

Total is 400 HzSlide41

Prescale

set used: 2E32 Hz/cm²

Sample: MinBias L1-skim 5E32 Hz/cm² with 10 Pile-up

Unpacking of L1 information,

early-rejection triggers

,

non-intensivetriggers

Mostly unpacking of calorimeter

info.

to form jets,

&

some muon triggers

Triggers with

intensive

tracking algorithms

Overflow: Triggers doing

particle flow

reconstruction (esp. taus)

Total HLT Time DistributionSlide42

Extension-1 of HLT Farm – 2011Slide43

Future HLT Upgrade OptionsSlide44

Requirements for LHC phases of the upgrades: ~2010-2020

Phase 1:

Goal of extended running in second half of the decade to collect ~100s/fb

80% of this luminosity in the last three years of this decade

About half the luminosity would be delivered at luminosities above the original LHC design luminosity

Trigger & DAQ systems should be able to operate with a peak luminosity of up to 2

x 1034Phase 2:Continued operation of the LHC beyond a few 100/fb will require substantial modification of detector elementsThe goal is to achieve 3000/fb in phase 2Need to be able to integrate ~300/fb-yrWill require new tracking detectors for ATLAS & CMSTrigger & DAQ systems should be able to operate with a peak luminosity of up to 5 x 1034Slide45

Detector Luminosity Effects

H

→ZZ → μμee, M

H

= 300 GeV for different luminosities in CMS

10

32 cm-2s-1

10

33

cm

-2

s

-1

10

34

cm

-2

s

-1

10

35

cm

-2

s

-1Slide46

CMS Upgrade

Trigger Strategy

Constraints

Output rate at 100 kHz

Input rate increases

x2

/x10 (Phase 1/Phase 2) over LHC design (1034)Same x2 if crossing freq/2, e.g. 25 ns spacing → 50 ns at 1034Number of interactions in a crossing (Pileup) goes up by x4/x20Thresholds remain ~ same as physics interest doesExample: strategy for Phase 1 Calorimeter Trigger (operating 2016+):Present L1 algorithms inadequate above 1034 or 1034 w/ 50 ns spacingPileup degrades object isolationMore sophisticated clustering & isolation deal w/more busy eventsProcess with full granularity of calorimeter trigger informationShould suffice for x2 reduction in rate as shown with initial L1 Trigger studies & CMS HLT studies with L2 algorithmsPotential new handles at L1 needed for x10 (Phase 2: 2020+)Tracking to eliminate fakes, use track isolation.Vertexing to ensure that

multiple

trigger objects come from

same interaction

Requires finer position resolution for calorimeter trigger objects for matching (provided by use of full granularity cal. trig. info.)Slide47

Phase 1 Upgrade Cal. Trigger Algorithm Development

Particle Cluster Finder

Applies tower thresholds to Calorimeter

Creates overlapped 2x2 clusters

Cluster Overlap Filter

Removes overlap between clusters

Identifies local maxima

Prunes low energy clusters

Cluster Isolation and Particle ID

Applied to local maxima

Calculates isolation deposits around 2x2,2x3 clusters

Identifies particles

Jet reconstruction

Applied on filtered clusters

Groups clusters to jets

Particle Sorter

Sorts particles

& outputs

the most energetic ones

MET,HT,MHT Calculation

Calculates Et Sums, Missing Et from

clusters

ECAL

HCAL

Δη

x

Δφ

=0.087x0.087

e

/

γ

ECAL

HCAL

τ

ECAL

HCAL

jet

η

φ

η

φ

η

φSlide48

Upgrade Algorithm Performance:Factor of 2 for Phase I

Factor of 2 rate reduction

Higher Efficiency

Isolated

electrons

Taus

Efficiency

QCD Rate (kHz)

Isolated

electrons

Taus

Efficiency

QCD Rate (kHz)

Phase 1 Algorithm

Present

Algorithm

Present

Algorithm

Present

Algorithm

Present

Algorithm

Phase 1 Algorithm

Phase 1 Algorithm

Phase 1 AlgorithmSlide49

uTCA Calorimeter Trigger Demonstrators



p

rocessing

cards with 160

Gb/s

input & 100 Gb/s output using 5 Gb/s optical links. four trigger prototype cards integrated in a backplane fabric to demonstrate running & data exchange of calorimeter trigger algorithms Slide50

CMS CSC Trigger Upgrades

Improve redundancy

Add station ME-4/2 covering

h

=1.1-1.8

Critical for momentum resolution

Upgrade electronics to sustain higher ratesNew Front End boards for station ME-1/1 Forces upgrade of downstream EMU electronicsParticularly Trigger & DAQ Mother BoardsUpgrade Muon Port Card and CSC Track Finder to handle higher stub rateExtend CSC Efficiency into h=2.1-2.4 regionRobust operation requires TMB upgrade, unganging strips in ME-1a, new FEBs, upgrade CSCTF+MPCME4/2Slide51

CMS

Level-1 Trigger



5x

10

34OccupancyDegraded performance of algorithmsElectrons: reduced rejection at fixed efficiency from isolationMuons: increased background rates from accidental coincidencesLarger event size to be read outNew Tracker: higher channel count & occupancy  large factorReduces the max level-1 rate for fixed bandwidth readout.Trigger RatesTry to hold max L1 rate at 100 kHz by increasing readout bandwidthAvoid rebuilding front end electronics/readouts where possibleLimits: readout time (< 10 µs) and data size (total now 1 MB)Use buffers for increased latency for processing, not post-L1AMay need to increase L1 rate even with all improvements

Greater burden on DAQ

Implies raising E

T

thresholds on electrons, photons, muons, jets and use of multi-object triggers, unless we have new information



Tracker

at L1

Need to compensate for larger interaction rate & degradation in algorithm performance due to

occupancySlide52

CMS

Level-1 Trigger



5x

10

34OccupancyDegraded performance of algorithmsElectrons: reduced rejection at fixed efficiency from isolationMuons: increased background rates from accidental coincidencesLarger event size to be read outNew Tracker: higher channel count & occupancy  large factorReduces the max level-1 rate for fixed bandwidth readout.Trigger RatesTry to hold max L1 rate at 100 kHz by increasing readout bandwidthAvoid rebuilding front end electronics/readouts where possibleLimits: readout time (< 10 µs) and data size (total now 1 MB)Use buffers for increased latency for processing, not post-L1AMay need to increase L1 rate even with all improvements

Greater burden on DAQ

Implies raising E

T

thresholds on electrons, photons, muons, jets and use of multi-object triggers, unless we have new information



Tracker

at L1

Need to compensate for larger interaction rate & degradation in algorithm performance due to

occupancySlide53

Tracking needed for L1 trigger

Muon L1 trigger rate

Single electron trigger rate

Isolation criteria are insufficient to reduce rate at

L =

10

35

cm

-2

.s

-1

5kHz @ 10

35

L = 10

34

L = 2x10

33

MHz

Standalone Muon trigger resolution insufficient

We need to get another x200 (x20) reduction for single (double) tau rate!

Amount of energy carried by tracks around

tau

/jet direction (PU=100)

Cone 10

o

-30

o

~d

E

T

/d

cos

q

Slide54

The Track Trigger Problem

Need to gather

information from 10

8

pixels in 200m

2

of silicon at 40 MHzPower & bandwidth to send all data off-detector is prohibitiveLocal filtering necessarySmart pixels needed to locally correlate hit Pt informationStudying the use of 3D electronics to provide ability to locally correlate hits between two closely spaced layersSlide55

3D Interconnection

Key

to

design

is

ability

of a single IC to connect to both top & bottom sensorEnabled by “vertical interconnected” (3D) technologyA single chip on bottom tier can connect to both top and bottom sensors – locally correlate informationAnalog information from top sensor is passed to ROIC (readoutIC) through interposerOne layer of chipsNo “horizontal” data transfer necessary – lower noise and powerFine Z information is not necessary on top sensor – long (~1 cm vs ~1-2 mm) strips can be used to minimize via density in interposerSlide56

Track Trigger Architecture

Readout designed to send all hits with P

t

>~2 GeV to trigger processor

High throughput –

micropipeline

architecture Readout mixes trigger and event data Tracker organized into phi segmentsLimited FPGA interconnectionsRobust against loss of single layer hitsBoundaries depend on pt cuts & tracker geometry Slide57

Tracking for electron trigger

Present CMS electron HLT

Factor of 10 rate reduction

: only tracker handle: isolation

Need knowledge of vertex

location to avoid loss of efficiency

- C. Foudas & C. SeezSlide58

Tracking for -jet isolation



-lepton trigger: isolation from pixel tracks outside signal cone & inside isolation cone

Factor of 10 reductionSlide59

CMS L1 Track Trigger for Muons

Combine with L1

 trigger

as is now done at HLT:

Attach tracker hits to improve P

T

assignment precision from 15% standalone muon measurement to 1.5% with the trackerImproves sign determination & provides vertex constraintsFind pixel tracks within cone around muon track and compute sum PT as an isolation criterionLess sensitive to pile-up than calorimetric information if primary vertex of hard-scattering can be determined (~100 vertices total at SLHC!)To do this requires  information on muons finer than the current 0.052.5°No problem, since both are already available at 0.0125 and 0.015°Slide60

CMS L1 Trigger Stages

Current for LHC:

TPG



RCT



GCT  GTProposed for SLHC (with tracking added): TPG  Clustering  Correlator SelectorTrigger PrimitivesRegional Correlation, Selection, Sorting

Jet Clustering

Seeded Track Readout

Missing E

T

Global Trigger, Event Selection Manager

e /

γ /τ/

jet

clustering

2x2,

φ

-strip ‘TPG’

µ track finder

DT, CSC / RPC

Tracker L1 Front End

Regional Track GeneratorSlide61

CMS Level-1 Latency

Present CMS Latency of 3.2

μsec = 128 crossings @ 40MHz

Limitation from post-L1 buffer size of tracker & preshower

Assume rebuild of tracking & preshower electronics will store more than this number of samples

Do we need more?

Not all crossings used for trigger processing (70/128)It’s the cables!Parts of trigger already using higher frequencyHow much more? Justification?Combination with tracking logicIncreased algorithm complexityAsynchronous links or FPGA-integrated deserialization require more latencyFiner result granularity may require more processing timeECAL digital pipeline memory is 256 40 MHz samples = 6.4 μsec Propose this as CMS SLHC Level-1 Latency baselineSlide62

CMS Trigger Summary

Level 1 Trigger

Select 100 kHz interactions from 1 GHz (10 GHz at SLHC)

Processing is synchronous & pipelined

Decision latency is 3

μ

sAlgorithms run on local, coarse data from Cal., MuonsProcessed by custom electronics using ASICs & FPGAsHigher Level Triggers: hierarchy of algorithmsLevel 2: refine using calorimeter & muon system info.Full resolution dataLevel 3: Use Tracking informationLeading to full reconstructionThe Future: SLHCRefined higher precision algorithms for Phase 1Use Tracking in Level-1 in Phase 2