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Page 1: Triggering CMS

Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 1

Triggering CMSWesley H. Smith

U. Wisconsin – MadisonCMS Trigger Coordinator

Seminar, Texas A&MApril 20, 2011

Outline:

Introduction to CMS Trigger Challenges & ArchitectureLevel -1 Trigger Implementation & PerformanceHigher Level Trigger Algorithms & PerformanceThe Future: SLHC Trigger

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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 2

LHC Collisions

with every bunch crossing23 Minimum Bias events

with ~1725 particles produced

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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 3

LHC Physics & Event RatesAt design L = 1034cm-2s-1

• 23 pp events/25 ns xing•~ 1 GHz input rate•“Good” events contain ~ 20 bkg. events

• 1 kHz W events• 10 Hz top events• < 104 detectable Higgs

decays/yearCan store ~ 300 Hz eventsSelect in stages

• Level-1 Triggers•1 GHz to 100 kHz

• High Level Triggers•100 kHz to 300 Hz

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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 rate

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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 5

CMS Detector Design

MUON BARREL

CALORIMETERS

PixelsSilicon Microstrips210 m2 of silicon sensors9.6M channels

ECAL76k 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

MUONENDCAPS

HCALPlastic scintillator/brasssandwich

Today:RPC |η| < 1.6 instead of 2.1 & 4th endcap layer missing

Level-1 Trigger Output• Today: 50 kHz

(instead of 100)

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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 HzFILTERED

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-1TRIGGER

DETECTOR CHANNELS

Challenges:1 GHz of Input InteractionsBeam-crossing every 25 ns with ~ 23 interactions produces over 1 MB of dataArchival Storage at about 300 Hz of 1 MB events

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Level 1 Trigger Operation

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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 8

CMS Trigger Levels

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L1 Trigger LocationsUnderground Counting Room•Central rows of racks fortrigger•Connections via high-speed copper links to adjacent rows of ECAL & HCAL readout racks with trigger primitive circuitry•Connections via opticalfiber to muon trigger primitive generatorson the detector•Optical fibersconnected via“tunnels” to detector(~90m fiber lengths)

Rows of Racks containing trigger & readout

electronics

7m thickshielding

wall

USC55

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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 10

CMS Level-1 Trigger & DAQOverall Trigger & DAQ Architecture: 2 Levels:Level-1 Trigger:

• 25 ns input• 3.2 μs latency

Interaction rate: 1 GHz

Bunch Crossing rate: 40 MHz

Level 1 Output: 100 kHz (50 initial)

Output to Storage: 100 Hz

Average Event Size: 1 MB

Data production 1 TB/day

UXC

U

SC

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CMS Calorimeter Geometry

EB, EE, HB, HE map to 18 RCT cratesProvide e/γ and jet, τ, ET triggers

1 trigger tower (.087η✕ .087φ) = 5 ✕ 5 ECAL xtals = 1 HCAL tower

2 HF calorimeters map on to 18 RCT crates

Trigger towers:Δη = Δϕ = 0.087

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ECAL Endcap GeometryMap non-projective x-y trigger crystal geometry

onto projective trigger towers:Individualcrystal

5 x 5 ECAL xtals ≠ 1 HCAL tower in detail

+ZEndcap

-ZEndcap

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Calorimeter Trig. Processing

Trigger Tower

25 Xtals (TT)

TCC(LLR)

CCS(CERN)

SRP(CEADAPNIA)

DCC(LIP)

TCSTTC

Trigger primitives

@800 Mbits/s

OD

DAQ

@100 kHz

L1

Global TRIGGER

RegionalCaloTRIGGER

Trigger Tower Flags (TTF)

Selective Readout Flags (SRF)

SLB (LIP)

Data path

@100KHz (Xtal Datas)

Trigger Concentrator Card

Synchronisation & Link Board

Clock & Control System

Selective Readout Processor

Data Concentrator Card

Timing, Trigger & Control

Trigger Control System

Level 1 Trigger (L1A)

From : R. Alemany LIP

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Calorimeter Trig.Overview(located in underground counting room)

CalorimeterElectronicsInterface

RegionalCalorimeter

Trigger

ReceiverElectron Isolation

Jet/Summary

Global Cal. TriggerSorting, ET

Miss, ΣET

GlobalTriggerProcessor

Global Muon TriggerIso 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 codeper 25 ns crossingUS 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-.195η, η>2.2)HF: 2✕(12 φ ✕ 12 η)

Copper 80 MHz Parallel4 Highest ET:Isolated & non-isol. e/γCentral, forward, τ jets,Ex, Ey from each crate

MinIon & QuietTags for each 4φ ✕ 4η region

GCT Matrix μ + Q bitsIC/LANL/UW

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ECAL Trigger Primitives

Test beam results (45 MeV per xtal):

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CMS Electron/Photon Algorithm

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CMS τ / Jet Algorithm

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L1 Cal. Trigger SynchronizationBX ID Efficiency – e/γ & Jets

• Sample of min bias events, triggered by BSC coincidence, with good vertex and no scraping

• Fraction of candidates that are in time with bunch-crossing (BPTX) trigger as function of L1 assigned ET

• Anomalous signals from ECAL, HF removed

• Noise pollutes BX ID efficiency at low ET values

e/γ

Jet/τ Forward Jet

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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 & ID• Conversion ID (inverse of conversion

rejection cuts) to select electron-like objects

• Efficiency 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 Correction

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Jet Trigger Efficiency

minimum-bias trigger jet energy correction: online / offline match turn-on curves steeper

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Reduced RE system|η| < 1.6

1.6

ME4/1

MB1

MB2

MB3

MB4

ME1ME2 ME3

*Double Layer

*RPC

Single Layer

CMS Muon Chambers

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Muon Trigger Overview|η| < 1.2 |η| < 2.40.8 < |η| |η| < 2.1

|η| < 1.6 in 2009

Cav

ern:

UX

C55

Cou

ntin

g R

oom

: US

C55

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CMS Muon Trigger Primitives

Memory to store patterns

Fast logic for matching

FPGAs are ideal

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CMS Muon TriggerTrack Finders

Memory to store patterns

Fast logic for matching

FPGAs are ideal Sort based on PT, Quality - keep loc.

Combine at next level - match

Sort again - Isolate?

Top 4 highest PT and quality muons with location coord.

Match with RPCImprove efficiency and quality

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DT

L1 Muon Trigger SynchronizationBX ID Efficiency – CSC, DT, RPC

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

RPC

CSC

Log Plot

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L1 Muon Efficiency vs. pT

01/04/2011

Barrel

EndCap

OverLap

L1_Mu7L1_Mu10L1_Mu12L1_Mu20

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CMS Global Trigger

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Global L1 Trigger Algorithms

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“Δelta” or “correlation” conditions

Unique Topological Capability of CMS L1 Trigger• separate objects in η & Φ:• Δ ≥ 2 hardware indices• ϕ: Δ ≥ 20 .. 40 degrees

Present Use:• eγ / jet separation to avoid

triggering twice on the same object in a correlation trigger

• objects to be separated by one empty sector (20 degrees)

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High Level Trigger Strategy

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All processing beyond Level-1 performed in the Filter FarmPartial event reconstruction “on demand” using full detector resolution

High-Level Trig. Implementation

8 “slices”

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Start with L1 Trigger Objects Electrons, Photons, τ-jets, Jets, Missing ET, Muons

• HLT refines L1 objects (no volunteers)Goal

• Keep L1T thresholds for electro-weak symmetry breaking physics• However, reduce the dominant QCD background

• From 100 kHz down to 100 Hz nominallyQCD background reduction

• Fake reduction: e±, γ, τ• Improved resolution and isolation: μ• Exploit event topology: Jets• Association with other objects: Missing ET• Sophisticated 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 events

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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 seed• Collect all sub-clusters in road η “super-cluster”

• Select highest ET cluster• Calorimetric (ECAL+HCAL) isolation

“Level-3” Photons• Tight 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-cluster

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“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 resonanceEfficiency = Npass/Nall

• Npass → number of probes passing the selection criteria• Nall → total number of probes counted using the resonance

Barrel Endcap

The efficiency of electron trigger paths in2010 data reaches 100% within errors

Electron (ET Thresh>17 GeV) with Tighter Calorimeter-basedElectron ID+Isolation at HLT

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Muon HLT & L1 EfficiencyBoth isolated & non-isolated muon trigger shown

• Efficiency loss is at Level-1, mostly at high-ηImprovement over these curves already done

• Optimization of DT/CSC overlap & high-η regions

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Jet HLT EfficiencyJet efficiencies calculated

• Relative to a lower threshold trigger• Relative to an independent trigger

Jet efficiencies plotted vs. corrected offline recoAnti-kT jet energy

• Plots are from 2011 run 161312

HLT_Jet370

BarrelEndcap All

HLT_Jet240

BarrelEndcap All

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

JetSingle Jet, DiJetAve,MultiJetQuadJet, ForwardJets, Jets+Taus

HTMisc. hadronic SUSY triggers

METBtag• MET triggers, Btag POG triggers

SingleMu• Single mu triggers (no had. requirement)

DoubleMu• Double mu trigger (no had. requirement)

SingleElectron• Single e triggers (no had. requirement)

DoubleElectron• Double e triggers (no had requirement)

PhotonPhotons (no had. requirement)

MuEGMu+photon or ele (no had. requirement)

ElectronHadelectrons + had. activity

PhotonHadPhotons + had. activity

MuHadMuons + had. activity

TauSingle and Double taus

TauPlusXX-triggers with taus

MuOniaJ/psi, upsilon+ Commisioning, Cosmics, MinimumBias

Expected rate of each PD is 15-30 Hz @ 5E32Writing a total of O(360) Hz. (Baseline is 300 Hz)

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Trigger Rates in 2011Trigger rate predictions based mostly on data.

• Emulation of paths via OpenHLT working well for most of trigger tableData 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

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Approx. evolution for some triggers

L=5E32• Single Iso Mu ET: 17 GeV• Single Iso elec ET: 27 GeV• Double Mu ET: 6, 6 GeV• Double Elec ET: 17, 8 GeV• e+mu ET: 17,8 & 8,17 GeV• Di-photon: 26, 18 GeV• e/mu + tau: 15, 20 GeV• HT: 440 GeV• HT+MHT: 520 GeV

L=2E33• Single Iso Mu ET: 30 GeV• Single Iso elec ET: 50 GeV• Double Mu ET: 10,10 GeV• Double Elec ET: 17, 8 GeV*• e+mu ET: 17,8 & 8,17 GeV*• Di-photon: 26, 18 GeV*• e/mu + tau: 20, 20-25 GeV• HT:• 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-up

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HLT at 1E33

Total is 400 Hz

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Prescale set used: 2E32 Hz/cm²Sample: 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 Distribution

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Extension-1 of HLT Farm – 2011

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Future HLT Upgrade Options

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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 1034

Phase 2:• Continued operation of the LHC beyond a few 100/fb will require

substantial modification of detector elements• The goal is to achieve 3000/fb in phase 2• Need to be able to integrate ~300/fb-yr• Will require new tracking detectors for ATLAS & CMS• Trigger & DAQ systems should be able to operate with a peak

luminosity of up to 5 x 1034

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Detector Luminosity Effects H→ZZ → μμee, MH= 300 GeV for different luminosities in CMS

1032 cm-2s-1 1033 cm-2s-1

1034 cm-2s-1 1035 cm-2s-1

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Wesley Smith, U. Wisconsin, April 20, 2011 Texas A&M Seminar: Triggering CMS - 46

CMS Upgrade Trigger StrategyConstraints

• 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 1034

• Number of interactions in a crossing (Pileup) goes up by x4/x20• Thresholds remain ~ same as physics interest does

Example: strategy for Phase 1 Calorimeter Trigger (operating 2016+):• Present L1 algorithms inadequate above 1034 or 1034 w/ 50 ns spacing

• Pileup degrades object isolation• More sophisticated clustering & isolation deal w/more busy events

• Process with full granularity of calorimeter trigger information• Should 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.)

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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

ECA

LHCAL Δη x Δφ=0.087x0.087

e/γ

ECA

L

HCAL

τ

ECA

L

HCAL

jet

ηφ

η

φ

η

φ

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Upgrade Algorithm Performance:Factor of 2 for Phase I

Factor of 2 rate reduction

Higher Efficiency

Isolated electrons Taus

Effic

ienc

yQ

CD

Rat

e (k

Hz)

Isolated electrons

Taus

EfficiencyQ

CD

Rate (kH

z)

Phase 1 Algorithm

PresentAlgorithm

PresentAlgorithm

PresentAlgorithm

PresentAlgorithm

Phase 1 Algorithm

Phase 1 Algorithm

Phase 1 Algorithm

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uTCA Calorimeter Trigger Demonstrators

processing 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

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CMS CSC Trigger UpgradesImprove redundancy

• Add station ME-4/2 covering η=1.1-1.8• Critical for momentum resolution

Upgrade electronics to sustain higher rates

• New Front End boards for station ME-1/1

• Forces upgrade of downstream EMU electronics• Particularly Trigger & DAQ Mother

Boards• Upgrade Muon Port Card and CSC

Track Finder to handle higher stub rate

Extend CSC Efficiency into η=2.1-2.4 region

• Robust operation requires TMB upgrade, unganging strips in ME-1a, new FEBs, upgrade CSCTF+MPC

ME

4/2

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CMS Level-1 Trigger 5x1034

Occupancy• Degraded performance of algorithms

• Electrons: reduced rejection at fixed efficiency from isolation• Muons: increased background rates from accidental coincidences

• Larger event size to be read out• New Tracker: higher channel count & occupancy large factor• Reduces the max level-1 rate for fixed bandwidth readout.

Trigger Rates• Try to hold max L1 rate at 100 kHz by increasing readout bandwidth

• Avoid rebuilding front end electronics/readouts where possible• Limits: readout time (< 10 µs) and data size (total now 1 MB)

• Use buffers for increased latency for processing, not post-L1A• May need to increase L1 rate even with all improvements

• Greater burden on DAQ• Implies raising ET 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 occupancy

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CMS Level-1 Trigger 5x1034

Occupancy• Degraded performance of algorithms

• Electrons: reduced rejection at fixed efficiency from isolation• Muons: increased background rates from accidental coincidences

• Larger event size to be read out• New Tracker: higher channel count & occupancy large factor• Reduces the max level-1 rate for fixed bandwidth readout.

Trigger Rates• Try to hold max L1 rate at 100 kHz by increasing readout bandwidth

• Avoid rebuilding front end electronics/readouts where possible• Limits: readout time (< 10 µs) and data size (total now 1 MB)

• Use buffers for increased latency for processing, not post-L1A• May need to increase L1 rate even with all improvements

• Greater burden on DAQ• Implies raising ET 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 occupancy

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Tracking needed for L1 triggerMuon L1 trigger rate

Single electron trigger rate

Isolation criteria are insufficient to reduce rate at L = 1035 cm-2.s-1

5kHz @ 1035

L = 1034

L = 2x1033

MH

z

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 10o-30o

~dE T

/dco

sq τ

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The Track Trigger Problem• Need to gather

information from 108 pixels in 200m2 of silicon at 40 MHz

• Power & bandwidth to send all data off-detector is prohibitive• Local filtering necessary• Smart pixels needed to

locally correlate hit Pt information

• Studying the use of 3D electronics to provide ability to locally correlate hits between two closely spaced layers

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3D InterconnectionKey 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 chips

No “horizontal” data transfer necessary – lower noise and power

Fine Z information is not necessary on top sensor – long (~1 cm vs ~1-2 mm) strips can be used to minimize via density in interposer

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Track Trigger ArchitectureReadout designed to send all hits with Pt>~2

GeV to trigger processor High throughput – micropipeline architecture Readout mixes trigger and event data Tracker organized into phi segments

• Limited FPGA interconnections• Robust against loss of single layer hits• Boundaries depend on pt cuts & tracker geometry

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Tracking for electron triggerPresent CMS electron HLT

Factor of 10 rate reductionγ: only tracker handle: isolation

• Need knowledge of vertexlocation to avoid loss of efficiency

- C. Foudas & C. Seez

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Tracking for τ-jet isolationτ-lepton trigger: isolation from pixel tracks

outside signal cone & inside isolation cone

Factor of 10 reduction

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CMS L1 Track Trigger for Muons

Combine with L1 μ trigger as is now done at HLT:•Attach tracker hits to improve PT assignment precision from 15% standalone muon measurement to 1.5% with the tracker•Improves sign determination & provides vertex constraints

•Find pixel tracks within cone around muon track and compute sum PT as an isolation criterion•Less 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 η information on muons finer than the current 0.052.5°•No problem, since both are already available at 0.0125 and 0.015°

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CMS L1 Trigger StagesCurrent for LHC:

TPG RCT GCT GTProposed for SLHC (with tracking added):

TPG Clustering Correlator SelectorTrigger Primitives

Regional Correlation, Selection, Sorting

Jet Clustering Seeded Track ReadoutMissing ET

Global Trigger, Event Selection Manager

e /γ /τ/jet clustering2x2, φ-strip ‘TPG’

µ track finderDT, CSC / RPC

Tracker L1 Front End

Regional Track Generator

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CMS Level-1 LatencyPresent 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 samplesDo 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 logic• Increased algorithm complexity• Asynchronous links or FPGA-integrated deserialization require

more latency• Finer result granularity may require more processing time• ECAL digital pipeline memory is 256 40 MHz samples = 6.4 μsec

• Propose this as CMS SLHC Level-1 Latency baseline

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CMS Trigger SummaryLevel 1 Trigger

• Select 100 kHz interactions from 1 GHz (10 GHz at SLHC)• Processing is synchronous & pipelined• Decision latency is 3 μs

• Algorithms run on local, coarse data from Cal., Muons• Processed by custom electronics using ASICs & FPGAs

Higher Level Triggers: hierarchy of algorithms• Level 2: refine using calorimeter & muon system info.

• Full resolution data• Level 3: Use Tracking information

• Leading to full reconstructionThe Future: SLHC

• Refined higher precision algorithms for Phase 1• Use Tracking in Level-1 in Phase 2


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