Transcript Document

High Level Triggering
Fred Wickens
High Level Triggering (HLT)
• Introduction to triggering and HLT systems
– What is Triggering
– What is High Level Triggering
– Why do we need it
• Case study of ATLAS HLT (+ some
comparisons with other experiments)
• Summary
2
Simple trigger for spark chamber set-up
S cintillator
0
-12kV
0
-12kV
0
-12kV
0
C1
P hoto-multiplier
C1
S park
Chamber
C2
Discriminator
And Gate
C2
Light
Guide
Discriminator
Amplifier
S park Gap
S park
Chamber
Logic signals
e.g. NIM
3
Dead time
• Experiments frozen from trigger to end of readout
– Trigger rate with no deadtime
= R per sec.
– Dead time / trigger
= t sec.
– For 1 second of live time = 1 + Rt seconds
– Live time fraction
= 1/(1 + Rt)
– Real trigger rate
= R/(1 + Rt) per sec.
Rate in Hz Dead time ms. Live time % Trigger rate Hz
10
1000
10
10
91
9.1
9.1
91
4
Trigger systems 1980’s and 90’s
• bigger experiments  more data per event
• higher luminosities  more triggers per
second
– both led to increased fractional deadtime
• use multi-level triggers to reduce dead-time
– first level - fast detectors, fast algorithms
– higher levels can use data from slower detectors
and more complex algorithms to obtain better
event selection/background rejection
5
Trigger systems 1990’s and 2000’s
• Dead-time was not the only problem
• Experiments focussed on rarer processes
– Need large statistics of these rare events
– But increasingly difficult to select the interesting events
– DAQ system (and off-line analysis capability) under
increasing strain - limiting useful event statistics
• This is a major issue at hadron colliders, but will also be
significant at ILC
• Use the High Level Trigger to reduce the
requirements for
– The DAQ system
– Off-line data storage and off-line analysis
6
Summary of ATLAS Data Flow Rates
• From detectors
> 1014 Bytes/sec
• After Level-1 accept
~ 1011 Bytes/sec
• Into event builder
~ 109 Bytes/sec
• Onto permanent storage
~ 108 Bytes/sec

~ 1015 Bytes/year
7
TDAQ Comparisons
8
The evolution of DAQ systems
9
Typical architecture 2000+
10
Level 1 (Sometimes called Level-0 - LHCb)
• Time:
one  very few microseconds
• Standard electronics modules for small systems
• Dedicated logic for larger systems
– ASIC - Application Specific Integrated Circuits
– FPGA - Field Programmable Gate Arrays
• Reduced granularity and precision
– calorimeter energy sums
– tracking by masks
• Event data stored in front-end electronics (at LHC
use pipeline as collision rate shorter than Level-1
decision time)
11
Level 2
• 1) few microseconds (10-100)
– hardwired, fixed algorithm, adjustable parameters
• 2) few milliseconds (1-100)
– Dedicated microprocessors, adjustable algorithm
• 3-D, fine grain calorimetry
• tracking, matching
• Topology
– Different sub-detectors handled in parallel
• Primitives from each detector may be combined in a
global trigger processor or passed to next level
12
Level 2 - cont’d
• 3) few milliseconds (10-100) - 2008
–
–
–
–
Processor farm with Linux PC’s
Partial events received with high-speed network
Specialised algorithms
Each event allocated to a single processor, large
farm of processors to handle rate
– If separate Level 2, data from each event stored in
many parallel buffers (each dedicated to a small
part of the detector)
13
Level 3
• millisecs to seconds
• processor farm
– microprocessors/emulators/workstations
– Now standard server PC’s
• full or partial event reconstruction
– after event building (collection of all data from all
detectors)
• Each event allocated to a single processor,
large farm of processors to handle rate
14
Summary of Introduction
• For many physics analyses, aim is to obtain as high
statistics as possible for a given process
– We cannot afford to handle or store all of the data a detector
can produce!
• What does the trigger do
– select the most interesting events from the myriad of events
seen
• I.e. Obtain better use of limited output band-width
• Throw away less interesting events
• Keep all of the good events(or as many as possible)
– But note must get it right - any good events thrown away are
lost for ever!
• High level trigger allows much more complex
selection algorithms
15
Case study of the ATLAS HLT system
Concentrate on issues relevant for
ATLAS (CMS very similar issues), but
try to address some more general
points
Starting points for any HLT system
• physics programme for the experiment
– what are you trying to measure
• accelerator parameters
– what rates and structures
• detector and trigger performance
– what data is available
– what trigger resources do we have to use it
17
Physics at the LHC
Interesting events are buried in a sea
of soft interactions
B physics
High energy QCD jet
production
top physics
Higgs production
18
The LHC and ATLAS/CMS
• LHC has
– design luminosity 1034 cm-2s-1 (In 2008 from 1030 - 1032 ?)
– bunch separation 25 ns (bunch length ~1 ns)
• This results in
– ~ 23 interactions / bunch crossing
• ~ 80 charged particles (mainly soft pions) / interaction
• ~2000 charged particles / bunch crossing
• Total interaction rate
– b-physics
– t-physics
– Higgs
fraction ~ 10-3
fraction ~ 10-8
fraction ~ 10-11
109 sec-1
106 sec-1
10 sec-1
10-2 sec-1
19
Physics programme
• Higgs signal extraction important but very difficult
• Also there is lots of other interesting physics
–
–
–
–
–
B physics and CP violation
quarks, gluons and QCD
top quarks
SUSY
‘new’ physics
• Programme will evolve with: luminosity, HLT capacity and
understanding of the detector
– low luminosity (2008 - 2009)
• high PT programme (Higgs etc.)
• b-physics programme (CP measurements)
– high luminosity (2010?)
• high PT programme (Higgs etc.)
• searches for new physics
20
Trigger strategy at LHC
• To avoid being overwhelmed use signatures with
small backgrounds
– Leptons
– High mass resonances
– Heavy quarks
• The trigger selection looks for events with:
–
–
–
–
Isolated leptons and photons,
t-, central- and forward-jets
Events with high ET
Events with missing ET
21
Example Physics signatures
Objects
Physics signatures
Electron 1e>25, 2e>15 GeV
Higgs (SM, MSSM), new gauge bosons,
extra dimensions, SUSY, W, top
Photon 1γ>60, 2γ>20 GeV
Higgs (SM, MSSM), extra dimensions,
SUSY
Muon 1μ>20, 2μ>10 GeV
Higgs (SM, MSSM), new gauge bosons,
extra dimensions, SUSY, W, top
Jet 1j>360, 3j>150, 4j>100 GeV
SUSY, compositeness, resonances
Jet >60 + ETmiss >60 GeV
SUSY, exotics
Tau >30 + ETmiss >40 GeV
Extended Higgs models, SUSY
22
Trigger
40 MHz
ARCHITECTURE
DAQ
Three logical levels
Hierarchical data-flow
LVL1 - Fastest:
Only Calo and Mu
Hardwired
On-detector
electronics:
Pipelines
~40 ms
LVL2 - Local:
LVL1 refinement +
track association
Event fragments
buffered in
parallel
~4 sec.
LVL3 - Full event:
“Offline” analysis
Full event in
processor farm
~2.5 ms
~ 200 Hz
Physics
~1 PB/s
(equivalent)
~ 300 MB/s
23
Selected (inclusive) signatures
Process
Level-1
2 em, ET>20 GeV
H0
H0Z Z* + – + – 2 em, ET>20 GeV
2 µ, pT>6 GeV
1 em, ET>30 GeV
1 µ, pT>20 GeV
2 em, ET>20 GeV
Z+–+X
2 µ, pT>6 GeV
1 em, ET>30 GeV
1 µ, pT>20 GeV
1 em, ET>30 GeV
t t  leptons+jets
1 µ, pT>20 GeV
W', Z'jets
1 jet, ET>150 GeV
SUSYjets
1 jet, ET>150 GeV
E miss
T
Level-2
2 , ET>20 GeV
2 e, ET>20 GeV
2 µ, ET>6 GeV, I
1 e, ET>30 GeV
1 µ, ET>20 GeV, I
2 e, ET>20 GeV
2 µ, ET>6 GeV, I
1 e, ET>30 GeV
1 µ, ET>20 GeV, I
1 e, ET>30 GeV
1 µ, ET>20 GeV, I
1 jet, ET>300 GeV
3 jet, ET>150 GeV
E miss
T
24
Trigger design - Level-1
• Level-1
– sets the context for the HLT
– reduces triggers to ~75 kHz
– has a very short time budget
• few micro-sec (ATLAS/CMS ~2.5 - much used in cable delays!)
• Detectors used must provide data very promptly,
must be simple to analyse
– Coarse grain data from calorimeters
– Fast parts of muon spectrometer (I.e. not precision
chambers)
– NOT precision trackers - too slow, too complex
– (LHCb does use some simple tracking data from their VELO
detector to veto events with more than 1 primary vertex)
– (CMS plans track trigger for sLHC - L1 time => ~6 micro-s)
– Proposed FP420 detectors provide data too late
25
ATLAS Level-1 trigger system
• Calorimeter and muon
– trigger on inclusive
signatures
• muons;
• em/tau/jet calo clusters;
missing and sum ET
• Hardware trigger
– Programmable
thresholds
– Selection based on
multiplicities and
thresholds
26
ATLAS em cluster trigger algorithm
“Sliding window”
algorithm repeated for
each of ~4000 cells
27
ATLAS Level 1 Muon trigger
RPC - Trigger Chambers - TGC
Measure muon
momentum with
very simple
tracking in a few
planes of trigger
chambers
RPC: Restive Plate Chambers
TGC: Thin Gap Chambers
MDT: Monitored Drift Tubes
28
Level-1 Selection
• The Level-1 trigger - an “or” of a large number of
inclusive signals - set to match the current physics
priorities and beam conditions
• Precision of cuts at Level-1 is generally limited
• Adjust the overall Level-1 accept rate (and the
relative frequency of different triggers) by
– Adjusting thresholds
– Pre-scaling (e.g. only accept every 10th trigger of a
particular type) higher rate triggers
• Can be used to include a low rate of calibration events
• Menu can be changed at the start of run
– Pre-scale factors may change during the course of a run
29
Example Level-1 Menu for 2x10^33
Level-1 signature
Output Rate (Hz)
EM25i
12000
2EM15i
4000
MU20
800
2MU6
200
J200
200
3J90
200
4J65
200
J60 + XE60
400
TAU25i + XE30
2000
MU10 + EM15i
100
Others (pre-scaled, exclusive, monitor, calibration)
Total
5000
~25000
30
Trigger design - Level-2
• Level-2 reduce triggers to ~2 kHz
– Note CMS does not have a physically separate Level-2 trigger, but
the HLT processors include a first stage of Level-2 algorithms
• Level-2 trigger has a short time budget
– ATLAS ~40 milli-sec average
• Note for Level-1 the time budget is a hard limit for every event, for the
High Level Trigger it is the average that matters, so a some events can
take several times the average, provided thay are a minority
• Full detector data is available, but to minimise resources
needed:
–
–
–
–
Limit the data accessed
Only unpack detector data when it is needed
Use information from Level-1 to guide the process
Analysis proceeds in steps with possibility to reject event after each
step
– Use custom algorithms
31
Regions of Interest
• The Level-1 selection is dominated by local
signatures (I.e. within Region of Interest RoI)
– Based on coarse granularity
data from calo and mu only
• Typically, there are
1-2 RoI/event
• ATLAS uses RoI’s to reduce
network b/w and processing
power required
32
Trigger design - Level-2 - cont’d
• Processing scheme
– extract features from sub-detector data in each
RoI
– combine features from one RoI into object
– combine objects to test event topology
• Precision of Level-2 cuts
– Emphasis is on very fast algorithms with
reasonable accuracy
• Do not include many corrections which may be applied
off-line
– Calibrations and alignment available for trigger not
as precise as ones available for off-line
33
ARCHITECTURE
Trigger
Calo
MuTrCh
40 MHz
40 MHz
LVL1
Muon
Trigger
ROD
ROIB
L
ROD
120
RoI’s
LVL2
~ 10 ms
RoI
requests
L2SV
ROB
ROD
GB/s
ROB
ROB
ROS
RoI data = 1-2%
L2P
L2P
L2P
T Event Filter
EFP
EFP
EFP
L2N
~2 GB/s
LVL2 accept
~ 1 sec
~ 1 PB/s
FE Pipelines
2.5 ms
LVL1 accept
75 kHz
~2 kHz
Other detectors
2.5 ms
Calorimeter
Trigger
H
DAQ
Read-Out Drivers
Read-Out Links
Read-Out Buffers
Read-Out Sub-systems
~3 GB/s
Event Builder
EB
~3 GB/s
EFN
~ 300 MB/s
~ 200 Hz
~ 300 MB/s
34
CMS Event Building
• CMS perform Event Building after Level-1
• This simplifies the architecture, but places
much higher demand on technology:
– Network traffic ~100 GB/s
• Use Myrinet instead of GbE for the EB network
• Plan a number of independent slices with barrel shifter to
switch to a new slice at each event
– Time will tell which
philosophy is better
35
Example for Two electron trigger
LVL1 triggers on two isolated
STEP 4
e/m clusters with pT>20GeV
Signature 
(possible signature: Z–>ee)
HLT Strategy:



Validate step-by-step
Check intermediate signatures
Reject as early as possible
Sequential/modular
approach facilitates
early rejection
STEP 3
Signature 
STEP 2
e30i
+
Iso–
lation
e30
Iso–
lation
+
pt>
30GeV
e
ecand
STEP 1
Cluster
shape
Level1 seed 
EM20i
e30
pt>
30GeV
+
track
finding
Signature 
e30i
e
track
finding
+
time
Signature 
ecand
Cluster
shape
+
EM20i
36
Trigger design - Event Filter / Level-3
• Event Filter reduce triggers to ~200 Hz
• Event Filter budget ~ 4 sec average
• Full event detector data is available, but to
minimise resources needed:
– Only unpack detector data when it is needed
– Use information from Level-2 to guide the process
– Analysis proceeds in steps with possibility to reject
event after each step
– Use optimised off-line algorithms
37
Electron slice at the EF
Wrapper of CaloRec
TrigCaloRec
EFCaloHypo
Wrapper of newTracking
matches electromagnetic
clusters with tracks and builds
egamma objects
EF tracking
EFTrackHypo
Wrapper of EgammaRec TrigEgammaRec
EFEgammaHypo
38
HLT Processing at LHCb
39
Trigger design - HLT strategy
• Level 2
– confirm Level 1, some inclusive, some semiinclusive,
some simple topology triggers, vertex
reconstruction
(e.g. two particle mass cuts to select Zs)
• Level 3
– confirm Level 2, more refined topology selection,
near off-line code
40
Example HLT Menu for 2x10^33
HLT signature
Output Rate (Hz)
e25i
40
2e15i
<1
gamma60i
25
2gamma20i
2
mu20i
40
2mu10
10
j400
10
3j165
10
4j110
10
j70 + xE70
20
tau35i + xE45
5
2mu6 with vertex, decay-length and mass cuts (J/psi, psi’, B)
10
Others (pre-scaled, exclusive, monitor, calibration)
20
Total
~200
41
Example B-physics Menu for 10^33
LVL1 :
•
•
•
MU6 rate 24kHz (note there are large uncertainties in cross-section)
In case of larger rates use MU8 => 1/2xRate
2MU6
LVL2:
•
•
•
•
•
Run muFast in LVL1 RoI ~ 9kHz
Run ID recon. in muFast RoI mu6 (combined muon & ID) ~ 5kHz
Run TrigDiMuon seeded by mu6 RoI (or MU6)
Make exclusive and semi-inclusive selections using loose cuts
– B(mumu), B(mumu)X, J/psi(mumu)
Run IDSCAN in Jet RoI, make selection for Ds(PhiPi)
EF:
•
•
•
Redo muon reconstruction in LVL2 (LVL1) RoI
Redo track reconstruction in Jet RoI
Selections for B(mumu) B(mumuK*) B(mumuPhi), BsDsPhiPi etc.
42
LHCb Trigger Menu
43
Matching problem
Background
Off-line
Physics
channel
On-line
44
Matching problem (cont.)
• ideally
– off-line algorithms select phase space which
shrink-wraps the physics channel
– trigger algorithms shrink-wrap the off-line selection
• in practice, this doesn’t happen
– need to match the off-line algorithm selection
• For this reason many trigger studies quote trigger
efficiency wrt events which pass off-line selection
– BUT off-line can change algorithm, re-process and
recalibrate at a later stage
• SO, make sure on-line algorithm selection is
well known, controlled and monitored
45
Selection and rejection
• as selection criteria are tightened
– background rejection improves
– BUT event selection efficiency decreases
1
select / reject fraction
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
0.8
1
cut value
select
reject
46
Selection and rejection
• Example of a ATLAS Event Filter (I.e. Level-3) study
of the effectiveness of various discriminants used to
select 25 GeV electrons from a background of dijets
47
Other issues for the Trigger
• Efficiency and Monitoring
– In general need high trigger efficiency
– Also for many analyses need a well known efficiency
• Monitor efficiency by various means
– Overlapping triggers
– Pre-scaled samples of triggers in tagging mode (pass-through)
• Final detector calibration and alignment constants not available
immediately - keep as up-to-date as possible and allow for the
lower precision in the trigger cuts when defining trigger menus
and in subsequent analyses
• Code used in trigger needs to be very robust - low memory
leaks, low crash rate, fast
• Beam conditions and HLT resources will evolve over several
years (for both ATLAS and CMS)
– In 2008 luminosity low, but also HLT capacity will be < 50% of full
system (funding constraints)
48
Summary
• High-level triggers allow complex selection procedures to
be applied as the data is taken
– Thus allow large numbers of events to be accumulated, even in
presence of very large backgrounds
– Especially important at LHC - but significant at most accelerators
• The trigger stages - in the ATLAS example
– Level 1 uses inclusive signatures
• muons; em/tau/jet calo clusters; missing and sum ET
– Level 2 refines Level 1 selection, adds simple topology triggers,
vertex reconstruction, etc
– Level 3 refines Level 2 adds more refined topology selection
• Trigger menus need to be defined, taking into account:
– Physics priorities, beam conditions, HLT resources
• Include items for monitoring trigger efficiency and calibration
• Must get it right - any events thrown away are lost for
ever!
49
Additional Foils
50
51
The evolution of DAQ systems
52
ATLAS Detector
53
ATLAS event - tracker end-view
54
Trigger functional design
• Level 1 Input 40 MHz Accept 75 kHz Latency 2.5 μs




Inclusive triggers based on fast detectors
Muon, electron/photon, jet, sum and missing ET triggers
Coarse(r) granularity, low(er) resolution data
Special purpose hardware (FPGAs, ASICs)
• Level 2 Input 75 (100) kHz Accept O(1) kHz Latency ~10 ms




Confirm Level 1 and add track information
Mainly inclusive but some simple event topology triggers
Full granularity and resolution available
Farm of commercial processors with special algorithms
• Event Filter Input O(1) kHz Accept O(100) Hz Latency ~secs
 Full event reconstruction
 Confirm Level 2; topology triggers
 Farm of commercial processors using near off-line code
55
CERN
computer
centre
Data
storage
SDX1
~30
Event rate
~ 200 Hz
Local
Storage
SubFarm
Outputs
(SFOs)
DataFlow
Manager
ATLAS Trigger / DAQ Data Flow
dual-socket server PC’s
~1600
~100
Event
Builder
Event
Filter
(EF)
SubFarm
Inputs
~ 500
LVL2
farm
(SFIs)
stores
LVL2
output
Gigabit Ethernet
Event data requests
Delete commands
Requested event data
Regions Of Interest
Event data
pulled:
partial events
@ ≤ 100 kHz,
full events
@ ~ 3 kHz
SDX1
pROS
Network
switches
Network switches
LVL2
Supervisor
Secondlevel
trigger
USA15
~150
PCs
Read-Out
Subsystems
(ROSs)
RoI
Builder
Timing Trigger Control (TTC)
USA15
Data of events accepted
1600 by first-level trigger
ReadOut
VME Dedicated links
Links
ReadOut
Drivers
(RODs)
UX15
ATLAS
detector
Firstlevel
trigger
Event data pushed @ ≤ 100 kHz,
1600 fragments of ~ 1 kByte each
UX15
56
Event’s Eye View - step-1
• At each beam crossing latch data into
detector front end
• After processing, data put into many parallel
pipelines - moves along the pipeline at every
bunch crossing, falls out the far end after 2.5
microsecs
• Also send calo + mu trigger data to Level-1
57
Event’s Eye View - step-2
• The Level-1 Central Trigger Processor combines the
information from the Muon and Calo triggers and
when appropriate generates the Level-1 Accept (L1A)
• The L1A is distributed in real-time via the TTC system
to the detector front-ends to send data from the
accepted event to the detector ROD’s (Read-Out
Drivers)
– Note must arrive before data has dropped out of the pipeline - hence hard dead-line of 2.5 micro-secs
– The TTC system (Trigger, Timing and Control) is a CERN
system used by all of the LHC experiments. Allows very
precise real-time data distribution of small data packets
• Detector ROD’s receive data, process and reformat it
as necessary and send via fibre links to TDAQ ROS
58
Event’s Eye View - Step-3
• At L1A the different parts of LVL1 also send
RoI data to the RoI Builder (RoIB), which
combines the information and sends as a
single packet to a Level-2 Supervisor PC
– The RoIB is implemented as a number of VME
boards with FPGAs to identify and combine the
fragments coming from the same event from the
different parts of Level-1
59
CERN
computer
centre
Data
storage
SDX1
~30
Event rate
~ 200 Hz
Local
Storage
SubFarm
Outputs
(SFOs)
DataFlow
Manager
ATLAS Level-2 Trigger
dual-socket server PC’s
~1600
~100
Event
Builder
Event
Filter
(EF)
SubFarm
Inputs
~ 500
LVL2
farm
(SFIs)
Gigabit Ethernet
Event data requests
Requested event data
Regions Of Interest
Event data for
Level-2 pulled:
partial events
@ ≤ 100 kHz
USA15
~150
PCs
Read-Out
Subsystems
(ROSs)
RoI
Builder
Region of Interest Builder (RoIB)
passes formatted information to one
of the LVL2 supervisors.
pROS
Network
switches
Network switches
LVL2
Supervisor
Secondlevel
trigger
Step-4
stores
LVL2
output
LVL2 supervisor selects one of the
processors in the LVL2 farm and
sends it the RoI information.
LVL2 processor requests data from
the ROSs as needed (possibly in
several steps), produces an accept
or reject and informs the LVL2
supervisor. Result of processing is
stored in pseudo-ROS (pROS) for an
accept.
Reduces network traffic to ~2 GB/s
c.f. ~150 GB/s if do full event build
LVL2 supervisor passes decision to
the DataFlow Manager (controls
Event Building).
60
CERN
computer
centre
Data
storage
SDX1
~30
Event rate
~ 200 Hz
Local
Storage
SubFarm
Outputs
(SFOs)
DataFlow
Manager
ATLAS Event Building
dual-socket server PC’s
~1600
~100
Event
Builder
Event
Filter
(EF)
SubFarm
Inputs
~ 500
LVL2
farm
pROS
Network
switches
Gigabit Ethernet
Event data requests
Delete commands
Requested event data
Regions Of Interest
Event data after
Level-2 pulled:
full events
@ ~3 kHz
USA15
~150
PCs
Read-Out
Subsystems
(ROSs)
RoI
Builder
Secondlevel
trigger
(SFIs)
Network switches
LVL2
Supervisor
Step-5
stores
LVL2
output
For each accepted event the
DataFlow Manager selects a SubFarm Input (SFI) and sends it a
request to take care of the building of
a complete Event.
The SFI sends requests to all ROSs
for data of the event to be built.
Completion of building is reported to
the DataFlow Manager.
For rejected events and for events for
which event Building has completed
the DataFlow Manager
sends "clears" to the ROSs (for 100 300 events Together).
Network traffic for Event Building is
~5 GB/s
61
~30
Local
Storage
SubFarm
Outputs
(SFOs)
DataFlow
Manager
~1600
~100
Event
Builder
Event
Filter
(EF)
SubFarm
Inputs
~ 500
LVL2
farm
pROS
Network
switches
Gigabit Ethernet
Network switches
LVL2
Supervisor
Secondlevel
trigger
(SFIs)
Event data requests
Delete commands
Event rate
~ 200 Hz
ATLAS Event Filter
dual-socket server PC’s
Requested event data
Data
storage
SDX1
Regions Of Interest
CERN
computer
centre
USA15
~150
PCs
stores
LVL2
output
Step-6
A process (EFD) running in each
Event Filter farm node collects each
complete event from the SFI and
assigns it to one of a number of
Processing Task’s in that node
The Event Filter uses more
sophisticated algorithms (near or
adapted off-line) and more detailed
calibration data to select events
based on the complete event data
Accepted events are sent to SFO
(Sub-Farm Output) node to be written
to disk
Read-Out
Subsystems
(ROSs)
RoI
Builder
62
~30
Local
Storage
SubFarm
Outputs
(SFOs)
DataFlow
Manager
~1600
~100
Event
Builder
Event
Filter
(EF)
SubFarm
Inputs
LVL2
farm
Secondlevel
trigger
(SFIs)
pROS
Network
switches
Gigabit Ethernet
Network switches
LVL2
Supervisor
Step-7
~ 500
Event data requests
Delete commands
Event rate
~ 200 Hz
ATLAS Data Output
dual-socket server PC’s
Requested event data
Data
storage
SDX1
Regions Of Interest
CERN
computer
centre
stores
LVL2
output
The SFO nodes receive the final
accepted events and writes them to
disk
The events include ‘Stream Tags’ to
support multiple simultaneous files
(e.g. Express Stream, Calibration, bphysics stream, etc)
Files are closed when they reach 2
GB or at end of run
USA15
~150
PCs
Read-Out
Subsystems
(ROSs)
Closed files are finally transmitted via
GbE to the CERN Tier-0 for off-line
analysis
RoI
Builder
63
ATLAS HLT Hardware
First 4 racks of HLT processors, each rack contains
- ~30 HLT PC’s (PC’s very similar to Tier-0/1 compute nodes)
- 2 Gigabit Ethernet Switches
- a dedicated Local File Server
64
ATLAS TDAQ Barrack Rack Layout
Shaft PX15
Cable Tray USA15
Racks enter v ia this door
Landing
350daN/m2
door
Row 4
Row 2
EF
EF
EF
EF
EF
EF
AIR FLOW
EF
EF
EF
EF
EF
EF
EF
FRONTs
EF
EF
EF
EF
EF
EF
3
EF
EF
EF
5
6
7
8
9
EF
EF
EF
EF
EF
EF
EF
EF
EF
EF
EF
12
13
EF
EF
EF
EF
EF
EF
EF
EF
The lower limit is due to the power
distribution boxes and will af f ect
most of the racks.
EF
EF
EF
EF
EF
EF
17
18
19
80-100 cm
e-box
e-box
11
EF
63 cm (taking into account the cooler)
16 Racks
10
EF
100 cm
18 Racks
FRONTs
e-box
4
EF
EF
17 Racks
BACKs
water pipes
Rack Number
The lower distance is due to structural
beams or v entillation f laps and and
applies to ~5 racks.
70-90 cm
door
Row 6
Ventilation duct (on the flor)
Landing
350daN/m2
door
14
15
16
Landing
350daN/m2
SDX Level 1 Layout
20
Crinoline Ladder
Se le ct w hich ye ar
SDX Level 2 Layout
Racks enter v ia this door
Landing
350daN/m2
Row 6
Row 4
Row 2
Ventilation duct (on the flor)
door
74-90 cm
FRONT
EF/L2 EF/L2
EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 NWbb NWbb T DCS cDCS DSS
2 Racks
AIR FLOW
BACKs
13 Racks
PP
63 cm (taking into account the cooler)
EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2 EF/L2
FRONTs
EF/L2 EF/L2 SFO
SFO
DC
SFI
SFI
SFI
18 Racks
100 cm
Backend
SFI
switch
DC switch
rack
DC rack
switch
Onlinerack
switchOnline
rack Online Online Online
17 Racks
water pipes
Rack Number
PP
3
e-box
4
5
6
80-100 cm
e-box
e-box
7
8
9
10
11
12
13
Flap Trap
2005
2006
2007
2008
2009
14
15
16
17
18
19
20
65
Naming Convention
First Level Trigger (LVL1) Signatures in
capitals e.g.
LVL1
HLT
type
e
electron
g
photon
MU
mu
muon
HA
tau
tau
fj
forward
jet
JE
je
jet energy
JT
jt
jet
TM
xe
missing
energy
threshold
EM
MU 20 I
name isolated
HLT in lower case:
threshold
EF in tagging
mode
mu 20 i _ passEF
name isolated
New in 13.0.30:
•
Threshold is cut value applied
•
previously was ~95% effic. point.
•
FJ
More details : see :https://twiki.cern.ch/twiki/bin/view/Atlas/TriggerPhysicsMenu
66
Min Bias Triggers
Min. Bias Trigger available for
the first time in 13.0.30.3
•
•
•
Based on SP Counting
Trigger if:
>40 SCT SP or > 900 Pixel
Clusters
Trigger if:
>40 SCT SP
or > 900 Pixels
clusters
To be done: add MBTS trigger
MBTS – Scintillators on the inside of
endcap calorimeter giving LVL1 info.
67
Electron Menu Coverage for L=1031cm-2s-1
16 LVL1 Thresholds for EM (electron, photon) & HA (tau)
EM3, EM7, EM13, EM13I, EM18, EM18I, EM23I, EM100
•s
Trigger
Single electron triggers
and pre-scaled triggers
with HLT pass-thru’ for
commissioning needs
Low mass pairs
Low-medium-pT
double/triple e-trigger
High-pT single e-trigger
(LVL1 pT~18 GeV)
Very high-pT e-trigger
Low pT single e-trigger
(LVL1 pT~7 GeV)
Physics coverage
Selections with isolated/non-isolated LVL1 thresholds
Triggers with L2 and/or EF pass-through
e.g. e15, e15i, e15_passHLT, e15i_passHLT, e20_passL2,
e20_passEF
J/, ee, DY are sources of isolated e with large stat.,
useful for calib. at low-pT, efficiency extraction at low-pT
e.g. 2e5, 2e10, e5+e7, e5+e10
Zee, Susy, new phenomena
e.g. 2e10, 2e15, 3e15
We, Zee, top, Susy, Higgs, Exotics etc.
Loose selections and lots of redundancy
e.g. e20, e20i, e25i, e15_xE20, e10_xE30, e105
Exotics, new phenomena e.g. em105_passHLT
Electrons from b,c decays (e typically not well isolated)
Useful for E/p studies. Need tighter cuts to limit rate
e.g. e12
Rate
5 Hz
6 Hz
5 Hz
5 Hz
1.5 Hz
17 Hz
68
Photon Menus for 1031
Trigger Item
Examples
Physics Coverage
Low pt item
HLT pre-scale 10 or
100
g10, g15, g15i
Hadronic calibration, inclusive and diphoton cross section
High pt item, no prescale
g20, g20i, g25, g25i
Direct photon, hadronic calibration
g105, g120
Exotics, SUSY, unknown, hadronic
calibration
Multi photon, no Isol.
no HLT prescale
2g10, 2g15, 2g20,
3g10
Di-photon cross section, Exotics, SUSY,
calibration
Triggers for
commissioning with
LVL1 prescale and
HLT in tagging mode
em15_passHLT,
em_15i_passHLT
g10_passL2
g10_passEF
Selections with/without L1 isolation,
triggers with L2/EF pass-through
Very high pt item non
isolated
Total rate (including overlaps) ~10 Hz
Rate
4 Hz
7 Hz
5 Hz
69
Muon Triggers
Six LVL1 thresholds : MU4, MU6, MU10, MU15, MU20, MU40
Isolation can be applied at the HLT
Triggers
Examples
Motivation
Rate
B-physics, J/, mm,
DY
4 Hz
Prescaled Low pT
single m
Unprescaled Low pT
dimuon
mu4, mu6
Prescaled triggers with
HLT pass-thru’
mu20i with calculating
but not applying
isolation
mu20_passHLT
commissioning
0.5 Hz
high pT triggers
with/without isolation
mu10, mu15, mu20,
mu20i, mu40
2mu10, 2mu20
high-pT physics: Z(mm),
Susy, Higgs, Exotics
etc.
20 Hz
2mu4, mu4+mu6,
2mu6
2.5 Hz
70
Bphysics
LVL1 + Muon at HLT
• 2mu4 : 2.5 Hz
• mu4 & mu6 pre-scaled : 4 Hz
LVL1 + ID & MU at HLT:
• mu4_DsPhiPi_FS, MU4_Jpsimumu_FS, MU4_Upsimumu_FS,
• MU4_Bmumu_FS, MU4_BmumuX_FS
Loose
selections
~10Hz
71
Tau Triggers
16 LVL1 Thresholds for EM (electron, photon) & HA (tau)
HA5, HA6, HA9I, HA11I, HA16I, HA25, HA25I, HA40
Signature
Example
Motivation
Single tau
prescaled
single tau
unprescaled
tau45, tau45i
Tau+MET
tau20i+xe30
W ->t at low luminosity and H−>t, 5 Hz
SUSY, etc at high lumi.
TauTau
2tau25i, 2tau35i
H->tautau
3 Hz
Z tt, preparation for 1033
SUSY, Charged Higgs
5 Hz
exotics and heavy Higgs
Rate
15 Hz
tau60, tau100
tau+e,mu,tau,jet tau20i_e10,
tau20i_mu10,
tau20i_j70,
tau20i_4j50,
tau20i_bj18
72
Single Jet Triggers
•
Strategy:
•
•
Initially use LVL1 selection with no active HLT selection and b-jet trigger in tagging mode
8 LVL1 Jet thresholds:
– Highest un-prescaled, value determined by rate considerations (Aim for ~20Hz)
– Other threshold set to equalize bandwidth across the ET spectrum
– Lowest threshold used to provide RoI for Bphysics trigger.
73
Jet Triggers (contd)
Triggers
Motivation
single jet
j5,j10,j18,j23,j35,j42,j70,j120,j200,j400
QCD, Exotics
multi-jet
3J10, 4J10, 3J18, 3J23, 4J18, 4J23, 4J35 searches pp->XX, X->jj, top, SUSY
forward jets
FJ10, FJ18,FJ26, FJ65, 2FJ10, 2FG26,
2FJ65, FJ65_FJ26
VBF
jet energy sum
JE280, JE340
SUSY
Trigger Rates for Forward Jets
Trigger Rates for multi-jets
74
Bjet Triggers
•
•
•
Jets tagged as B-jets at HLT based on track information
Will allow lower LVL1 jet thresholds to be used
For initial running the Bjet triggers will be in tagging mode. Active selection will be switched
on once the detector & trigger are understood.
75
Missing ET, Total SumET
8 LVL1 Missing ET thresholds
76
Combined Triggers
• Menu contains large no. combined signatures
Type
Examples
Motivation
tau+e, tau+mu, e+mu
tau15i_e10,
tau25i_mu6,
tau20i_mu10, e10_mu6
tt, SUSY
tau+Missing ET
tau45_xe40,
tau45i_xe20
W, tt, SUSY, exotics
tau+jet
tau25i_j70
W, tt, SUSY, exotics
mu+jet
mu4_j10
exotics
jet + missing ET
j70_xe30
SUSY, exotics
Total Rate 46 Hz
77
Total Rates
LVL1
Rate (Hz)
LVL1
47,000
LVL2
865
EF
200
EF
LVL2
15
78