Nikos Varelas
University of Illinois at Chicago
L2Cal Group at UIC:
Mark Adams
Bob Hirosky
Rob Martin
Nikos Varelas
Marc Buehler (graduate student)
James Heinmiller (undergraduate)
Mike Klawitter (part time engineer)
2/6/99
L2 Review
NV/UIC
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 L2Cal Crate and I/O
 Status of L2Cal Algorithms:
 Jets
 Electrons
 Missing ET
 Timing of Algorithms
 Summary
2/6/99
L2 Review
NV/UIC
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• From Calorimeter via FIC/MBT:
10 input cables with 304 Bytes/cable
– Header
– L1 Seed Tower Bit Masks for EM and Total
– L1 Tower ET data for EM and Total
• From SCL via MBT:
– L1 accept (3 Bytes)
– L1 Qualifiers (2 Bytes)
•
•
•
•
•
•
•
L2Jet Needed
L2Em Needed
L2Etmiss Needed
3 Spare Bits
Unbiased Sample
Forced Write
Collect Status
– L2Global accepts
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• To L3
– For normal events send the L2Global output
– For UBS or Forced Write events the full L1
input and L2Cal output will be sent
• To L2Global
– About 136 Bytes/event (including headers)
– Will be fine tuned when algorithms are finalized
based on input from physics/Id groups
• Each worker will preface its data with a
12Byte header
– Header will include information about the
processing status (i.e., format errors, timeouts
etc) of the event
• Each worker will complete transmission
with a 4 Byte trailer
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L2 Review
NV/UIC
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All L2Cal algorithms will use a low-threshold reference
set of L1 0.2x0.2 trigger towers as input for clustering.
L1 EM ET - Rounded in 0.25 GeV steps
L1 Tot ET - Sum of EM and HAD truncated in
0.5 GeV steps
jet
L2Cal Processors
electron
neutrino
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L2 Review
NV/UIC
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• The algorithm:
Start w/ list of jet seed towers from L1
• For each seed tower, cluster ET of the surrounding 5x5 (or 3x3)
tower array
• Add to Jet list all clusters whose ET sum exceeds a min threshold
• ET order the Jet list (descending order)
• Eliminate Jets failing overlap restriction
If ET(A) > ET(C) ; keep A,B
If ET(C) > ET(A) ; keep C,B
• Event Samples used in simulations:
– Data: W-> JJ triggers from Run 1C Global
Runs with Lum = 17E30
– MC: UPG GEANT inclusive jet events w/
generated thresholds: (2,5,10,20,40,80 GeV)
overlapped with: (1,3,5,7) additional MB
interactions (not overlapped with noise)
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L2 Review
NV/UIC
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W->JJ Data
Tower Seed Distributions
Threshold 
RMS
1.0 GeV
40
20
1.5 GeV
17
7
2.0 GeV
9
4
For a high-ET (>350GeV) jet data sample:
 = 20, RMS= 6 for L1(1,2)
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L2 Review
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W->JJ Data
L2 Jet Distributions
2/6/99
L2 Review
NV/UIC
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Measured w/ MC - UPG Geant sample
Pjet and Cal Jet matching methods:
1) Projection Method
calorimeter
PJet
Project PJet axis into
calorimeter.
Does corresponding
seed/cluster ET pass
imposed cuts?
2) Matching Method
(run L2Jet algorithm)
Compare L2Jets to PJets
Look for matches
calorimeter
PJet
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DR<0.5?
L2 Review
NV/UIC
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L2Jet Efficiency for seeds/clusters
Effs. for seed/cluster cuts and
Algorithm(seed cut,cluster cut)
Reference algorithm L1(1,2) L2(1,10)
2/6/99
Central jets
L2 Review
NV/UIC
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L2Jet Rate Estimates
• Method:
– First weight MC events appropriately
1) use JETRAD to bridge all h PJet Cross Section to
central inclusive jet CS in data
2) estimate total MC event cross section for PJet
ET>5 GeV; ~ 1/11 Min Bias cross section
– Calculate trigger rate as ~ fraction of MB events
passing imposed threshold(s)
(# events passing threshold ) x (weight)

Rate 
(# events in sample ) x (weight)
1

11
• Plot L2Jet Efficiency vs Rate for 20 and
100 GeV PJets.
– Compare L2 3x3 jet algorithm to 5x5 version
– Measure Eff. vs Rate w/ and w/o L2 clustering
– Examine the effects of 0.5 GeV truncation to triggertower ETs
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L2 Review
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3 = 3x3 algorithm
5 = 5x5 algorithm
Eff. vs Rate at 20 GeV
L2 thresholds (1,10)(1,8)(1,6)(1,4)(none)
5x5
L1(1,1.5)
3x3
L1(1,2)
L1 only
• ~ factor of 3 rate reduction w/ 20% eff. cost
• no strong cluster size preference
• need to tune the MC further so we can study/improve
the algorithm for low-ET jets
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3 = 3x3 algorithm
5 = 5x5 algorithm
Eff. vs Rate at 100 GeV
L2 thresholds (1,60)(1,50)(1,40)(1,30)(none)
L1(1,7)
L1(1,9)
L1 only
• order of magnitude rate reduction easily attainable
at L2 w/o loss in efficiency
• no strong cluster size preference
2/6/99
L2 Review
NV/UIC
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Effects of L1 Total-ET Truncation for
20 GeV Jets
L2 (1,4)
w/ 0.5 GeV truncation
L1 (1,2)
L2 (1,8)
L2 (1,6)
L2 (1,10)
0.25 GeV rounding
L2 (1,12)
L2 (1,15)
the effect of L1 energy truncation can be accommodated
at L2 by choosing lower jet thresholds
2/6/99
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An Example at Lum=1E32
Level-0
Eff at 100 GeV
45 mb x 1E32 = 4.5 MHz
L1(1,9)
~ 96%
6.7 KHz
L1(1,12)
<L2(1,30)>
~ 92%
130 Hz
1800 Hz
for same Eff
2/6/99
L3
L2 Review
NV/UIC
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• The algorithm:
Start w/ list of EM seed towers from L1
• For each seed tower, determine nearest neighbor w/ the largest ET
• Calculate the following summed ET : quantities:
1) ET(EM) of seed tower + largest neighbor
2) ET(Total) of seed tower + largest neighbor
3) sum ET(Total) of 3x3 trigger towers centered on seed
tower
• Order surviving candidates in descending ET(EM)
Apply cuts on ET(EM), EM fraction, and
Isolation
• Event Samples used in simulations:
– Single electrons uniformly distributed in f, in the forward
region: 1.9<|h|<2.3
– ISAJET dijet events with various thresholds starting at
2 GeV
Events were processed through UPG_GEANT with two (on
average) additional interactions (not overlapped with noise)
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Courtesy Mrinmoy Bhattacharjee
• L1 Cuts:
– FPS: 0.3 MIPs (upstream)
5 MIPs (downstream)
U view matching
V view matching
– CAL: EM trigger tower above threshold
– Match FPS with CAL L1 Tower in Quadrant
• L2 Cuts:
– FPS: Require downstream U and V view
matching -> convert to h, f in 0.2 x 0.2 bins
– CAL: Find EM cluster using NN algorithm.
Apply EM fraction and Isolation cuts.
– Match FPS track to EM cluster within
Df x Dh = 0.3 x 0.3
• No rounding/truncation applied to L1
tower energies
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L2 Review
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Forward electrons
Eff. vs Background Rate at 18 GeV
preliminary
L2 thresholds (1,15)(1,12)(1,10)(none)
L1 (1,7)
L1 (1,7)
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L2 Review
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Forward electrons
Eff. vs Background Rate at 18 GeV
preliminary
L2 thresholds (1,17)(1,15)(1,12)(none)
L1 (1,10)
L1 (1,10)
2/6/99
L2 Review
NV/UIC
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Forward electrons
Eff. vs Background Rate at 30 GeV
preliminary
L2 thresholds (1,15)(1,12)(1,10)(none)
L1 (1,7)
L1 (1,7)
w/ FPS match
order of magnitude rate reduction attainable at L2 w/
small cost in efficiency
2/6/99
L2 Review
NV/UIC
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Forward electrons
Eff. vs Background Rate at 30 GeV
preliminary
L2 thresholds (1,17)(1,15)(1,12)(none)
L1 (1,10)
L1 (1,10)
w/ FPS match
order of magnitude rate reduction attainable at L2 w/
small cost in efficiency
2/6/99
L2 Review
NV/UIC
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• Candidates will be sorted in descending ET
•
order
Information per candidate
–
–
–
–
–
–
–
–
eta
phi
ET
eta center
phi center
eta leading TT
phi leading TT
Spare
• Total 12 Bytes/object
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L2 Review
(1 Byte)
(1 Byte)
(2 Bytes)
(1 Byte)
(1 Byte)
(1 Byte)
(1 Byte)
(4 Bytes)
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• Candidates will be sorted in descending ET
•
order
Information per candidate
–
–
–
–
–
–
–
–
–
–
eta
phi
ET
EM fraction
Isolation Fraction
eta leading TT
phi leading TT
eta other TT
phi other TT
Spare
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L2 Review
• Total 12 Bytes/object
(1 Byte)
(1 Byte)
(2 Bytes)
(1 Byte)
(1 Byte)
(1 Byte)
(1 Byte)
(1 Byte)
(1 Byte)
(2 Bytes)
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• Need input from physics groups
• Information per event
–
–
–
–
Missing ETX
Missing ETY
Scalar ET
Spare
• Total 16 Bytes/event
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(2 Bytes)
(2 Bytes)
(2 Bytes)
(10 Bytes)
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• The algorithm:
Loops over all towers within prescribed h range, calculating
the vector ET sum of all towers with ET > Min_Tow_ET. It
returns the X and Y components of the Missing ET.
• Possible Enhancements:
– Calculate Scalar ET using the same cuts as for
Vector ET
– Calculate ET for more than one set of Tower
cuts
– Calculate ET using different threshold for each
Tower
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• Code:
– written in C
– compiled with C or C++ compiler on DEC
Alpha workstation running UNIX (timing results
roughly the same)
– Executable down-loaded and run on UIC
PC164 evaluation board containing DEC
21164 Alpha processor with 500MHz clock
• Event Sample:
– MC Dijet data generated with ISAJET
– Data block Structure as planned for hardware
• 10 “cable blocks” containing:
*
*
*
*
2/6/99
EM Tower Seed Mask
Total Tower Seed Mask
EM Tower ET data
Total Tower ET data
L2 Review
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Jet proc time vs # seeds
35
30
Time (us)
25
20
15
10
5
Average seed range
0
0
5
10
15
20
25
30
# Level 1 seeds
Time (s) ~ 2.5 + 1.12 x (# seeds)
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Time (s) ~ 2 + 2.3 x (# seeds)
2/6/99
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MET Mean Processing time
40
39
38
Mean Time (us)
37
36
35
34
33
32
31
30
0
200
400
600
800
1000
1200
1400
Mean # Tow ers
The average time for 0.5 GeV
Tower ET threshold is ~ 33 s
2/6/99
L2 Review
All Towers above
threshold
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• We have a fully designed L2Cal
Preprocessor system which has sufficient
CPU power to execute reasonable L2
algorithms with < few % deadtime
– if more power needed, can add up to two
Workers for parallel processing
• We have working versions of
•
•
Jets/Electron/Missing ET algorithms
which offer acceptable rate reduction
The data movement architecture is
complete and the monitoring path has
been established (see previous talks)
We request TDR approval
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L2 Review
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