STT simulations Horst Wahl, 25 February 2000

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STT simulations(Horst Wahl, 25 February 2000)
Outline

• trigger simulation
• (Silvia Tentindo-Repond, Sailesh Chopra, John
  Hobbs, with help from Brian Connolly, Harrison
  Prosper, Dave Toback)
• queueing studies
• (Stephan Linn)

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STT trigger simulation(Silvia Tentindo-Repond,
Sailesh Chopra,...)

• STT trigger simulator
• integral component of D0 RunII Trigger Simulator
• tasks
• simulate all components of the STT
• hit clustering (STC)
• CTT road information handling (FRC)
• hit filtering (STC)
• tracking (TFC)
• provide tool for optimization of
• trigger parameters and algorithms
• monitoring parameters
• provide tool for determination of efficiencies
• L2STT Simulator code split into three packages
• tsim_l2stt (main package)
• l2stt_util
• l2stt_fitting (for detailed studies of track
  fitting algorithms)

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STT simulation status

• presently available functionality
• SMT hit clustering
• cluster algorithm
• so far, only one algorithm implemented
  neighbor clustering without cap on clustersize,
  (same alg. as used in L3, but different from
  algorithm being studied for firmware
  implementation)
• other algorithms foreseen
• hit filter
• CTT roads now integrated into main package
• temporarily, use analytic expression for
  translation from CFT to SMT coordinates
• first version of LUT (translation map) available
  (but based on nominal position -- will need
  possibility to use real positions)
• tracking (with John Hobbs, Wendy Taylor)
• l2stt_fitting contains all possible tracking
  algorithms (for testing)
• main package will only have final choice of
  algorithm
• still being debugged
• test output
• create a text file that contains SMT hits in
  cable-format, to be used as an input for
  debugging and testing of VHDL code for
  clustering. (RCP switch)
• CTT roads to be done
• most of the code committed to CVS t70

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Clusters from t tbar events

• only from barrels

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Clusters from Z?b bbar 2 min.bias events

• barrel only

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Clusters vs SMT layer from Z?b bbar 2 min.bias
events
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• Clusters from one t tbar event

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• one t tbar event
• road centers in SMT
• SMT clusters in CTT roads

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CTT tracks from Z?b bbar 2 min.bias events

• Clusters in roads
• nb. of CTT tracks

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Queueing Studies(Stephan Linn)

• Questions to be answered by queueing studies
• how much processing (e.g. track fitting) time
  can we afford before deadtime becomes
  unacceptably high?
• where are the potential bottlenecks in the data
  flow through the trigger?
• additional buffering needed?
• Queueing simulation software
• previously, used RESQ (IBM product)
• not supported anymore, only runs on IBM platforms
  ? look for alternative
• Ptolemy
• simulation package developed by EE and
  comp.science dept. at UC-Berkeley
• can simulate complex systems at different levels
  of detail and with different time scales
• elements of system represented by queue and
  serve galaxies
• specified by service time and queue depth
• event defined by starting time and data value
  (event number)

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STT Model in Ptolemy

• use available specifications
  (note by U.Heintz at
  http//physics.bu.edu/heintz/STT_q.pdf)
• parameterize (from MC data)
• Nt number of tracks per sextant
• Nh number of hits per detector
• H clusters per hit
• T clusters per track
• transmission speeds
• data sizes
• model
• STT modeled as 6 independent sectors
• random numbers Nt, (hyperexponential) Nh (double
  gaussian), track fitting time (double
  exponential, from JHWT studies)
• correlations between module delay times (depend
  on Nt, Nh)
• PCI bus arbitration (priority to road transfer
  over filtered clusters)
• STC filter waits for roads from FRC
• (see draft of note by Stephan Linn at
  http//www-d0.fnal.gov/linn/d0_private/queue.ps
  )

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STT Queueing model
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PCI bus model
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distributions used

• cluster multiplicity
• track multiplicity

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Queuing simulation results

• latency
• for one STT sextant

• latency for one sextant reproduces track fit
  delay
• full system latency worst-of-N convolution with
  five other sextants
• total deadtime lt 1 (for nominal values)
  (not counting deadtime due to min.
  time between L1 accept)
• 16 event buffer before track fitting takes care
  of 50?s track fitting time -- never filled to
  capacity.
• no additional buffer necessary

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Parameters in queueing simulation

• Parameters used in simulation
• number of hits per detector Nh double gaussian
  with mean 36, max. 90 (corresponds to 8
  overlapped jet-brew events, with L1 trigger pt
  gt 7 GeV, plus 2 addl occupancy for noise)
• number of L1CTT tracks per sextant Nt
  hyper-exponential with mean 2 , rms 4, max
  32 (corresponds to 6 overlapped jet-brew
  events, with L1 trigger pt gt 7 GeV)
• number of hits per cluster H gaussian with
  mean 3.6, rms 2.8 (from t tbar events)
• timing for tracking double exponential, with
  old values, i.e. 15?s
• notes
• changing Nt to 4.8 with rms 8, other
  parametes unchanged deadtime lt 2
• Z ? b bbar 2 MB events
• Nt 1.5 (9 per event with rms 5),
• Nh 9, H 3.9
• for 8 overlapped jet-brew events, Nt 3.7, rms
  6.0
• time for track fitting now much shorter than that
  used
• for 396ns bunch spacing
• for L 0.8 x 1032cm2 s-1 mean nb. of int.
  2.3 prob. of 7 int. 1
• for L 2.0 x 1032cm2 s-1 mean nb. of int.
  5.4 prob. of 7 int. 12, of 8 8

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Probability of N(interactions)/crossing

• For L 0.8 x 1032cm2 s-1

N(int) 36 bunch 99 bunch
0 0.11219921 0.45137941
1 0.24543345
0.35904841 2
0.2684403 0.142802 3
0.19573587 0.03786381
4 0.10704204 0.00752966
5 0.04683045
0.00119789 6
0.01707344 0.00015881 7
0.0053354 1.8046E-05
8 0.00145888 1.7944E-06
1 or more 0.88780079
0.54862059 2 or more 0.64236734
0.18957218 4 or more 0.17819117
0.00890638 8 or more 0.00190983
1.9666E-06 ltNgt 2.18747933
0.79544703
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Probability of N(interactions)/crossing

• For L 2.0 x 1032cm2 s-1

N(int) 36 bunch 99 bunch
0 0.00421672 0.13688453 1
0.02305996 0.27221098 2
0.06305397 0.27066177 3
0.11494105 0.17941425 4
0.15714448 0.08919658 5
0.17187515 0.03547558 6
0.15665555 0.01175789 7
0.122386 0.00334028 8
0.08366151 0.00083032 1 or more
0.99578328 0.86311547 2 or more
0.97272333 0.5909045 4 or more
0.79472831 0.14082848 8 or more
0.18666714 0.00105815 ltNgt
5.46869832 1.98861757
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TFC timing

• From minimum bias jet-brew with L1 pt gt 7GeV,
  get mean number and standard deviation for CTT
  tracks
• parameterize Nt distribution by double
  exponential with ? 2?
• integration of this function allows estimate of
  P(Nt lt16) for given number of overlapping
  interactions
• for L 2.0 x 1032cm2 s-1 , and 396ns bunch
  crossing time, prob. of gt 7 interactions is 18
  for 8 interactions, prob. of more than 16 tracks
  4 ? negligible effect on deadtime.

Nint ?(Nt) ?(Nt) P(Nt
lt 16) 1 0.8 1.5
? 1 2 1.0
1.9 ? 1 4 1.1
2.1 0.997 6
2.0 4.3 0.981 8
3.7 6.0
0.957
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Simulation summary

• STT trigger simulation tools close to being ready
  and useful
• tracking part operational
• alternative clustering schemes to be implemented
• LUT for hitfilter to be done
• work on providing test output in progress
• caveat need to ensure that algorithms in trig.
  simulation correspond to firmware implemented in
  hardware.
• queueing simulation package operational
• have STT queueing model which is quite realistic
• studies so far show no major bottleneck in
  design even for high luminosities and
  occupancies
• can easily adapt to new specifications as design
  progresses
• more detailed TFC simulation in progress