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Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

1

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 Trigger

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

2

LHC Collisions

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

3

LHC Physics & Event Rates

At design
L

= 10
34
cm
-
2
s
-
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


< 10
4

detectable Higgs
decays/year

Can store ~ 300 Hz events

Select in stages


Level
-
1 Triggers


1 GHz to 100 kHz


High Level Triggers


100 kHz to 300 Hz

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

4

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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

5

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)

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

6

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 events

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

7

Level 1 Trigger Operation

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

8

CMS Trigger Levels

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

9

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 generators

on the detector


Optical fibers

connected via

“tunnels” to detector

(~90m fiber lengths)

Rows of Racks containing
trigger & readout
electronics

7m thick

shielding

wall

USC55

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

10

CMS Level
-
1 Trigger & DAQ

Overall 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千

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

11

CMS Calorimeter Geometry

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

Provide e/


and jet,

E
T

triggers

1 trigger tower (.087



.087

⤠= 5


5 䕃AL x瑡ls = 1 HCAL 瑯wer

2 HF calorimeters map on to 18 RCT crates

Trigger towers:

Δη

=
Δ
ϕ

= 0.087

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

12

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

+Z

Endcap

-
Z

Endcap

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

13

Calorimeter Trig. Processing

TCC

(LLR)


CCS

(CERN)

SRP

(CEA

DAPNIA)

DCC

(LIP)

TCS

TTC

OD

DA
Q

@100
kHz

L1

Global TRIGGER

Regional

CaloTRIGGER

Trigger Tower Flags
(TTF)

Selective Readout
Flags (SRF)

SLB
(LIP)

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 LIP

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

14

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




60


H/ECAL

Towers (.087
 


.087
 
for


< 2.2 &

.174
-
.195

,

>2.2)

HF: 2

(12




12

)

Copper 80 MHz Parallel

4 Highest E
T
:

Isolated & non
-
isol
.
e/


Central, forward,


jets,

E
x
,
E
y

from each crate

MinIon

& Quiet

Tags for

each 4




4


region

GCT Matrix


μ

+ Q bits

IC/
LANL
/UW

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

15

ECAL Trigger Primitives

Test beam results (45 MeV per xtal):

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

16

CMS Electron/Photon Algorithm

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

17

CMS


/ e琠Algri瑨m

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

18

L1 Cal. Trigger Synchronization

BX 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 E
T



Anomalous signals from ECAL, HF removed



Noise pollutes BX ID efficiency at low E
T

values

e/
γ


Jet/
τ


Forward Jet

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

19

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

E
T

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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

20

Jet Trigger Efficiency


minimum
-
bias trigger


jet energy correction: online / offline match


turn
-
on curves steeper

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

21

Reduced RE
system

|

| < 1.6

1.6

ME4/1

MB1

MB2

MB3

MB4

ME1

ME2

ME3

*Double
Layer

*RPC

Single Layer

CMS Muon Chambers

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

22

Muon Trigger Overview

|
η| < 1.2

|
η| < 2.4

0.8 <
|
η|

|
η| < 2.1

|
η| < 1.6
in 2009

Cavern: UXC55

Counting Room: USC55

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

23

CMS Muon Trigger Primitives

Memory to store patterns

Fast logic for matching


FPGAs are ideal

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

24

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
-

match

Sort again
-

Isolate?

Top 4 highest P
T

and
quality muons with
location coord.

Match with RPC


Improve efficiency and quality

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

25

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

Plot

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

26

L1 Muon Efficiency vs.
p
T

01/04/2011

Barrel

EndCap

OverLap

L1_Mu7

L1_Mu10

L1_Mu12

L1_Mu20

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

27

CMS Global Trigger

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

28

Global L1 Trigger Algorithms

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

29


Δ
elta” 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:


e
γ

/ jet separation to avoid
triggering twice on the same
object in a correlation trigger


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



Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

30

High Level Trigger Strategy

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

31

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”

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

32

Start with L1 Trigger Objects

Electrons, Photons,

-
jetsⰠetsⰠMissing E
T
, 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 nominally

QCD background reduction


Fake reduction: e
±
,



Improved resolution and isolation:



Exploit event topology: Jets


Association with other objects: Missing E
T


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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

33

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




in narrow
η
-
window
around seed


Collect all sub
-
clusters in road
η

“super
-
cluster”


Select highest E
T

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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

34

“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 criteria


Nall

→ total number of probes counted using the resonance

Barrel

Endcap

The efficiency of electron trigger paths in

2010 data reaches 100% within errors

Electron (ET Thresh>17 GeV) with Tighter Calorimeter
-
based

Electron
ID+Isolation

at HLT

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

35

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

regions

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

36

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
-
k
T

jet energy


Plots are from 2011 run 161312

HLT_Jet370

Barrel

Endcap

All

HLT_Jet240

Barrel

Endcap

All

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

37

Summary of Current Physics Menu

(5E32) by Primary Dataset

Jet


Single Jet,
DiJetAve,MultiJet


QuadJet
,
ForwardJets
,
Jets+Taus

HT


Misc.
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)


Photon

Photons (no
had.
requirement)

MuEG

Mu+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

MuOnia

J/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)

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

38

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 scenarios

Emulated &

Online Rates:


Agreement to



30
%,

data
-
only check of
measured
rate

vs
. separate emulation

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

39

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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

40

HLT at 1E33

Total is 400 Hz

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

41

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 Distribution

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

42

Extension
-
1 of HLT Farm


2011

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

43

Future HLT Upgrade Options

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

44

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

10
34

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

10
34


Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

45

Detector Luminosity Effects


H
→ZZ → μμee, M
H
= 300 GeV for different luminosities in CMS

10
32

cm
-
2
s
-
1

10
33

cm
-
2
s
-
1

10
34

cm
-
2
s
-
1

10
35

cm
-
2
s
-
1

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

46

CMS Upgrade
Trigger Strategy

Constraints


Output rate at 100 kHz


Input rate increases

x2
/x10 (Phase
1/Phase 2)
over LHC design (10
34
)


Same x2 if crossing freq/2, e.g. 25 ns spacing → 50 ns at 10
34


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
10
34

or 10
34
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 algorithms

Potential 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.)

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

47

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

φ

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

48

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
Algorithm

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

49

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


Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

50

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 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
h
㴲⸱
-
2⸴ reg楯n


Robust operation requires TMB
upgrade,
unganging

strips in ME
-
1a,
new
FEBs
, upgrade CSCTF+MPC

ME4/2

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

51

CMS
Level
-
1 Trigger




34

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:

readut

瑩me


⠼ 10 
s
⤠and da瑡 size ⡴瑡l nw 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 E
T

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

qracker

a琠L1


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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

52

CMS
Level
-
1 Trigger




34

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:

readut

瑩me


⠼ 10 
s
⤠and da瑡 size ⡴瑡l nw 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 E
T

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

qracker

a琠L1


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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

53

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



Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

54

The Track Trigger Problem


Need to gather

information from 10
8

pixels in 200m
2


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 P
t

information


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




Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

55

3D Interconnection

Key
to

design
is

ability
of a single IC to
connect to both

top &
bottom sensor

Enabled by “vertical interconnected”
(3D) technology

A single chip on

bottom
tier can

connect to both top and bottom

sensors


locally correlate information

Analog information from

top

sensor is passed to ROIC

(readout

IC) through interposer

One 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


Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

56

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 segments


Limited FPGA interconnections


Robust against loss of single layer hits


Boundaries depend on p
t

cuts & tracker
geometry


Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

57

Tracking for electron trigger

Present CMS electron HLT








Factor of 10 rate reduction


: nly tracker handle: islatin


Need knowledge of vertex

location to avoid loss of efficiency

-

C.
Foudas

& C.
Seez

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

58

Tracking for

-
je琠isla瑩n


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

Factor of 10 reduction

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

59

CMS L1 Track
Trigger for Muons

Combine with L1


trigger

as is nw dne at HLq:


Attach tracker hits to improve P
T

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 P
T

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
h

infr浡tin n 浵ns
finer than the current 0.05

2.5
°


No problem, since both are already available at 0.0125
and 0.015
°

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

60

CMS L1 Trigger Stages

Current for LHC:


TPG


RCq


GCq




Proposed for SLHC (with tracking added):


TPG


Clustering


Crrelatr

Selectr

Trigger Primitives

Regional Correlation, Selection, Sorting

Jet Clustering

Seeded Track Readout

Missing E
T

Global Trigger, Event Selection Manager

e /

jet

clustering

2x2,

-
strip ‘TPG’

µ track finder

DT, CSC / RPC

Tracker L1 Front End

Regional Track
Generator

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

61

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 frequency

How 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

Wesley Smith, U. Wisconsin,

April 20, 2011

Texas A&M
Seminar: Triggering CMS
-

62

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

s


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 reconstruction

The Future: SLHC


Refined higher precision algorithms for Phase 1


Use Tracking in Level
-
1 in Phase 2