L3 Filtering: status and plans for the near future

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L3 Filtering status and plans for the near future

• D? Collaboration Meeting 25th April 2002
• Dan Claes and Terry Wyatt,
• on behalf of the L3 Algorithms group.

For more details see, e.g., L3 talk at trigger
workshop http//www-d0.fnal.gov/computing/algorit
hms/level/docs/L3_workshop.ppt
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Within a month
Currently

Time budget for L3 i/o, event building, filtering
? 100 nodes/500 s 0.2 s
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Level 3 Jargon

• Tool Does the real work
• Unpacks raw data, finds tracks, clusters
• Identifies physics objects (e, ?, ?, jet ,?, W,
  Z)
• Filter Applies (simple) cuts on objects
• e.g. pt(?) gt 5 GeV
• Filter Script Defines a L3 trigger condition
• Logical .AND. of one or more filters
• e.g. pt(?) gt 5 GeV .AND. pt(jet) gt 10 GeV
• If all filters in a script are .TRUE. trigger is
  satisfied and event is recorded
• Mark and Pass
• Selects unbiased sample of input events to be
  recorded

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• In order to save processing time
• Only a partial reconstruction of each event is
  performed, depending on the L1/L2 trigger
  information
• For each L1/L2 trigger that fires
• One or more L3 filter scripts run
• Each script calls the filters/tools necessary for
  the trigger decision
• Tool results are kept in case they are needed
  again in that event
• Details of which filters/tools are called by each
  script
• determined by the triggerlist
• and performed by ScriptRunner
• Author Moacyr Souza (Fermilab/LAFEX)
• L3 central code management Jon Hays (Imperial)

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L3TMuon (local muon track reconstruction)
original author Paul Balm (NIKHEF)
current responsibles Christophe Clement
(Stockholm) ,
Martijn Mulders (Fermilab),
Martin Wegner (Aachen)
L3TMuon uses much of the offline muon reco code

• Short term goal to run a filter L3FMuon
• with loose quality
• cutting on pT
• Mainly needed for single muon triggers
• (which currently have a L1 prescale of 40)

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L3TMuon

• Dynamic unpacker commissioned (p11.04.00)
• Longstanding memory leak fixed (p11.04.00)
• Keeping up with updates to the offline muon
  reco code
• new memory leak and timing problems
• temporary fixes by adjusting rcp parameters
• L3FMuon has been run online in special runs

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Timing

• p11.04.01 default rcp parameters
• (maxopt version running on 1 GHz PIII)
• mean time/event 200 ms
• when run online 50 out of 200,000
• events took more than 30 seconds to
• process

• p11.04.01 parameters tuned to reduce
• time taken
• - number of A/BC segments considered
• - extrapolation step size
• - number of track-fit iterations
• mean time/event 20 ms
• eliminates time-outs

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Efficiency (pT 5 GeV Monte Carlo single muons)
?
Default RCP parameters
Loose L3 muon Tight L3 muon
?
Tuned RCP parameters
?
Notes Loose efficiency 80 (cf.
geometrical acceptance 90) Poor tight
efficiency in central region (track fit fails
to converge also seen in offline reco.)
?
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Rejection measured on data single muon test runs
central
forward
default parameters
tuned parameters
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Next Steps for L3FMuon

• Thursday 24th April
• another single muon test run taken
• (with tuned parameters)
• showed no signs of timing or memory problems
• Get L3FMuon running online full-time
• Global_CalMuon6.00 exits with loose L3FMuon
  hanging off L1 single muon and muon-jet triggers
  (100 MarkPass)

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Next Steps for L3FMuon

• Fix muon reco memory leak
• Optimise parameters for L3
• Memory/timing efficiency/rejection
• Find out why some events take so long to
  reconstruct
• Stricter procedures for production releases of
  offline muon reco software
• Including a specific requirement for L3FMuon
  tests BEFORE code changes released to production
  branch
• Comparison L2 ? L3 (e.g., efficiency, momentum
  resolution)
• Longer term We need a serious analysis of the
  cost/benefit of retaining/breaking the link
  between L3TMuon and muon reco

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Recent progress in L3 central tracking

• Offline quality unpacking and geometry for L3
• Improved SMT-CFT matching
• stand-alone tracking filter
• track-based primary vertex tool

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SMT/CFT Unpacking and Geometry
Principal author Robert Illingworth (Imperial
College)

• SMT unpacker
• Fully dynamic, parameterized pedestals, noisy
  strip killing
• CFT unpacker
• replace global threshold with individual channel
  thresholds
• up to date thresholds and cable maps
• Offline quality geometry implemented for SMT and
  CFT in L3
• (Released in p11.06.00)
• When improved thresholds/cable maps/geometry are
  available
• requires no code changes
• but care in archiving/version-tagging (general
  problem!)

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Level 3 Global Track Finding author Daniel
Whiteson (Berkeley)

• Find axial CFT tracks
• Match stereo CFT clusters
• Extend into SMT
• Require 8/8 axial CFT hits if no matched axial
  SMT hits
• Require 7/8 axial CFT hits if ?3 matched axial
  SMT hits
• If CFT axial/stereo match fails
• CFT-SMT match done in xy-only
• but SMT stereo information still used to give 3D
  tracking
• (new feature implemented in p11.06.00)

CFT Tracking Algorithm - L3TCFTTracker
Principal author Ray Beuselink (IMPERIAL)
P11 tool certification
Robert Illingworth and Chris Barnes (IMPERIAL)
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Current L3 global tracking performance
track ? (rad)
z at dca (cm)
CFT only
Number of axial hits on track
Number of stereo hits on track
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Comparison of L3 and offline tracking
number of tracks
track ? (rad)
q/pT (GeV-1)
dca (cm)
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Timing for global track tool
Time per event (ms) (d0mino - debug version)
about 8 ms per event for unpack tools (1 GHz P3
maxopt)
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Next steps for central tracking

• Test p11.06.00 version on most recent available
  data
• Get it running online full-time!
• Measure efficiency vs. rejection rate of
  stand-alone track filter on, e.g., single muon
  events

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A possible plan for filtering on
single muon triggers
We could require an .OR. of

• EITHER Loose L3 muon
• OR Central track
• (i.e., using redundancy to improve efficiency)
• N.B. Tracking will not be perfect for a long time
• (If you dont like this, you can always exclude
  these event by using the L3 trigger names)
• Longer term
• May need to require track-muon match (at least
  for low pT)
• Tool exists (Paul Balm)
• Also investigate track-Calorimeter MIP match
• Tool under development (Martin Grünewald)

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L3 Primary Vertex needed soon!
1) Histogram technique using SMT hits
author Guilherme Lima (UERJ/Brazil)
Has yet to be fully tested on REAL
DATA Opportunity for new person to get involved!
2) Track-based L3TVertexFinder
author Ray Beuselinck (Imperial) testing Chris
Barnes, Per Jonsson (Imperial)
Recently upgraded to use either CFT or Global
candidate tracks as input N.B. Marseille group
(Arnaud Duperrin, Mossadek Talby, Eric Kajfasz)
hope to be actively involved in testing tracking,
vertexing.
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Monte Carlo Performance
efficiency
purity Z ??? 75
99 tt 95
95 (to find a vertex within 1 cm of the
correct primary)
?z residual in Z ??? events
?z (cm)
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Reconstructed vertex position in real data
40 of events have a vertex reconstructed
z (cm)

• Next steps
• tune cuts on numbers of hits required
  (especially for SMT stereo hits)
• finish certification

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L3TEle Electron Tool authors Volker
Buescher (Mainz) Ulla
Blumenschein (Mainz)

• Current filter
• simple 0.25 cone
• applying cuts on
• ET
• e.m. fraction (gt0.9)
• transverse shower shape
• ?,? energy weighted cluster axis
  position

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Efficiency in Monte Carlo Events
Electron ET (GeV)
Electron ET (GeV)
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Comparison of data and single electron Monte
Carlo (trigsim)trigger turn-on curve
Efficiency ()
Electron ET (GeV)
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Single electron triggers

• At L1 we have two (unprescaled) single electron
  triggers
• CEM(1,10)
• CEM(2,5)
• At L3 we run the same two single electron
  filters
• pT gt 15 GeV, emfrac gt 0.9
• pT gt 12 GeV, emfrac gt 0.9, shower shape
• Combined rejection factor 3.5
• We do a similar thing with CEM(1,5)
• (heavily prescaled)

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Further developments for single electron triggers

• More sophisticated treatment of transverse and
  longitudinal shower shape
• Studies in progress
• Add in parallel to the two current filters
• Higher pT cut and softer e.m. fraction cut?
• Stand-alone track filter?
• Matched track looser e.m. cuts?
• (Matched pre-shower looser e.m. cuts)?
• Do we have enough L3 trigger bits (256)?
• Alternative have one filter that combines all
  available information (with details of the
  trigger decision stored in L3PhysicsResults)
• When we have to cut harder (soon) this redundancy
  will help to maintain
• High efficiency
• Small systematic error

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L3TJet Tool
author Volker Buescher (Mainz)
high precision calorimeter readout available at
L3 sharpen the turn-on curve
e.g., fraction of events passing L3FJet(1,15)
pT of leading offline JCCA jet (GeV)

• running online stably since early Sept01
• rejection factors 20-50 for different triggers

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Next Steps (p11.07)

• Use primary vertex ?
• Calorimeter non-linearity corrections implemented
  in
• calorimeter unpacker (Marumi Kado)
• Killing of hot cells implemented
• (Marumi Kado, Gregorio Bernardi have
  implemented
• NADA into L3)

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L3FTauHadronic Level3 TauTool
author Gustaaf Brooijmans (Fermilab) current
responsible Yann Coadou (Upsala)
Based on calorimeter jet shape variables
QCD
Z???
Running online since Jan-2002 Example mu1ptxatxx_
CJT(1,3) L3Tau (pT gt 10 GeV) gives rejection
factor 5.5 Next step switch on tracking
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Other tools on a longer timescale

• missing ET
• tools to associate objects in different detectors
  (e.g. track to muon)
• cps and fps cluster finding and unpacking
• b-tag impact parameter, secondary vertex
• tools to calculate "physics" quantities
• (e.g., inv. mass, delta_eta)
• tools to identify physics event types
• (e.g., W, Z, stream definitions)
• Keep raw data on reco output of W/Z candidates?
• Many opportunities for new people to get
  involved!

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L3 Monitoring

• L3 filter statistics for each trigger available
  to shift crew via daq_monitor
• L3 reconstruction results written out with the
  raw data
• l3fanalyze program produces rootuple
• Used offline for
• testing new code versions
• checks of data quality
• Plan to run online as examine use root to
  fill monitoring histograms from rootuple

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Monitoring

• Extra person(s) urgently needed to work on this!
• macros to define monitoring histograms
• common job submission on standard test samples to
  exercise all the L3 tools/filters (and L2?)
• migration to online
• "bit-wise" on/offline check
• matching L3 objects to MC/L1/L2/reco objects
• L3 monitoring needs to get a lot more systematic
  and routine!

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Can we do more sophisticated online monitoring in
the L3 nodes?

• For example, collect histograms, measure
  efficiencies
• L3 does a pretty complete reconstruction of the
  data
• Make use of the 95 of the events that we reject?
  
• Measure trigger turn-on curves (for L1 and L2 as
  well as L3)
• Do background studies
• (Why write out events and have the huge overhead
  in having to
• run offline reconstruction and storing them
  permanently if
• they are needed for relatively simple
  operations that can
• be performed adequately in L3?)
• Write out a stream with L3PhysicsResults and no
  raw data?
• Write out an insurance or not for reco
  stream?
• Best way to concatenate results from monitor
  processes running on each of the 100 L3 farm
  nodes not worked out yet.

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Will require extra resources at L3, but the
potential return (in terms of spotting trigger
problems and in saving offline resources) might
make this a very cost-effective investment. This
will also be the case if we find that lack of cpu
power is limiting the sophistication of the event
reconstruction and/or filtering that is possible
in L3.
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L3 central infrastructure opportunities for new
people to get involved

• Scriptrunner central L3 code infrastructure,
  release management
• Calibration/alignment technical infrastructure
  
• L3 reconstruction results on thumbnail
• Streaming
• Development of "user" and "physics analysis"
  tools

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Conclusions, outlook.

• Currently
• Calorimeter-based filtering (jets, electrons,
  taus) only
• Factor 5 rejection needed at L3
• Next steps (p11.06) to commission
• Muons, central tracking, track-based primary
  vertexing, calorimeter non-linearity and hot cell
  killing.
• Within a month
• DAQ improvements L3 input rate 500 Hz.
• In the next few months
• L1 tracks, L1 calorimeter acceptance and large
  tiles
• L2 rejection increasing
• L3 input rate 1000 Hz
• Higher luminosity
• Lots of interesting challenges and scope for new
  people

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To find out more

• L3 Algorithms web-pages
• http//www-d0.fnal.gov/computing/algorithms/level3
  /home.html
• L3 Algorithms working group meetings take place
  every week
• Wednesday 1400-1530 in the Farside
• Talk to Dan Claes (dclaes_at_unlhep.unl.edu) or
• Terry Wyatt (twyatt_at_fnal.gov) about the
• opportunities to get involved!