Simulation and PFA Simulation and PFA Development Efforts at NIU: Development Efforts at NIU: Status & Plans Status & Plans D. Chakraborty, for the NIU ILC detector group Main contributors: V. Zutshi, G. Lima, J. McCormick, R. McIntosh Fermilab, 22 Sep 2005
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Simulation and PFA Development Efforts at NIU: Status & Plans D. Chakraborty, for the NIU ILC detector group Main contributors: V. Zutshi, G. Lima, J.
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Simulation and PFA Simulation and PFA Development Efforts at NIU: Development Efforts at NIU:
Status & PlansStatus & PlansD. Chakraborty, for the NIU ILC detector
group
Main contributors:
V. Zutshi, G. Lima, J. McCormick, R. McIntosh
Fermilab, 22 Sep 2005
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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OutlineOutline• Simulation
– GEANT4-based packages: LCDG4, TBMokka, (SLIC)
– Parametric simulation of GeV-to-ADC: DigiSim
• Particle-Flow Algorithms
– Density-weighted Clustering in Calorimeter
• Calorimeter-only (no track-seeding)
• Same for ECal (e, , and HCal (h+, h0 ).
– Replace cal clusters with matching (MC) tracks, if any.
• The Directed Tree Algorithm
– Association of isolated “fragment”s or “satellite”s.
• Work in Progress and Future Plans
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Simulation: SummarySimulation: Summary• Primarily interested in exploring the (semi-)digital
hadron calorimeter option in general, with scintillator as the active material in particular.
• When we started, there was no GEANT4-based simulation package to produce output compatible with the Java-based reconstruction framework.
• LCDG4 was written at NIU starting from a LCDROOT developed at U. Colorado. LCDG4 fully conformed with all standard I/O requirements (geometry input & event output formats), offered new features like non-projective geometry & better links to MC truth, fixed many bugs. (GL,RM)
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Simulation: Summary Simulation: Summary (contd.)(contd.)• NIU collaborated with DESY,LLR to produce
TBMokka, derived from Mokka (the G4-based TESLA simulator) for simulation of the CALICE TB module. NIU also produced a stand-alone G4-based application for cross-check. (JM)
• Thoughts on what is now SLIC started while JM was at NIU. JM was on SLAC-NIU joint appointment when SLIC was written.
• DigiSim allows easy parametric simulation of the many effects between the G4 energy deposits and recorded data. Available in Java & C++. (GL)
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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TasksTasks
• Full-detector simulation:
LCDG4 (for ALCPG)
• Test-beam module simulation:
TBMokka (with DESY/LLR, for CALICE)
• Simulation of detector imperfections:
DigiSim (for ALCPG, CALICE, …)
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Full detector simulation:Full detector simulation: LCDG4LCDG4
• GEANT4 v7.0.• Most hadronic physics lists available,
LCPhysics not tested yet.• Input format: binary STDHEP• Output format: .lcio (standard) or .sio
(Gismo compatible)• Nominal American detector geometries
are implemented via XML geometry files (continuous tubes+disks only).
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4: some nice LCDG4: some nice featuresfeatures
• Correct MC particle hierarchy, even when V0s and hyperon decays are forced at the event generation stage.
• Energies deposited in absorbers are available for cross-checks.
• Non-projective geometries available.
• Simple analysis code and documentation available from CVS and http://nicadd.niu.edu/~lima/lcdg4/.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4: Projective vs. non-LCDG4: Projective vs. non-projectiveprojective
• Barrel only.
• Rectangular virtual cells with linear dimensions, controlled at run time (XML).
• Ecal and HCal can be made projective or non-projective independently.
projective non-projective
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4: XML geometry descriptionLCDG4: XML geometry description
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4 output: general LCDG4 output: general featuresfeatures
• One particle collection and several hit collections (one hit collection per subdetector)
• Each hit points to the contributing particles (except tracker hits from calorimeter back-scatters).– LCIO only: (x,y,z) coordinates stored for every hit
• All secondaries above an energy threshold (now set at 1 MeV), except for shower secondaries, are saved in output with:– Particle id and generation/simulation status codes.– Production momentum, production* and ending position
(*LCIO only).– Calorimeter entrance: position and momentum (SIO
only).– Pointers to parent particles.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4: LCDG4: zoom in on primary zoom in on primary interactioninteraction
0
0 →0 0
0
ΛK
s0
Decaysforced ingenerator correctlyprocessed
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4: example: LCDG4: example: e+e- tt
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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LCDG4: wrap-upLCDG4: wrap-up• Being replaced by SLIC as the the
ALCPG standard, but many analysis packages have yet to adapt to the new standards.
• Code with doc + instructions available:http://nicadd.niu.edu/~lima/lcdg4
• Many interesting single particle and full event samples available, new ones can be requested:
For detailed access instructions, see http:// nicadd.niu.edu/~jeremy/admin/scp/index.html
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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DigiSimDigiSim• Goal: a program to simulate the signal collection and
digitization process in the ILC detector(s).
• Converts the GEANT4 output (energy depositions and space-time coordinates) into the same format AND as close as possible to real data from readout channels.
• Same code can then be used to process MC & real data.
• Serves a convenient and standardized hook for the user to model such detector effects as inefficiencies, non-uniformities, non-linearities, attenuation, noise, cross-talk, hot and dead channels, cell ganging, etc. involved in signal collection, propagation, and conversion/recording.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Requirements and Requirements and choiceschoices
• Basic requirements:– Object-oriented design to simplify
maintenance and implementation of new functionality
– Should be usable for both ALCPG’s Java-based reco framework and CALICE’s MARLIN (C++)
– To be tested for TB simulation– Usable in stand-alone and preprocessor modes
• In stand-alone mode, it produces LCIO events in the sae format as real data. All input information is preserved.
• In preprocessor mode, doesn’t produce any persistent output, event in memory passed on to reconstruction.
– Very easy to configure and enhance through text-based driver files.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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DigiSim event loopDigiSim event loop
Modifiers
TempCalHitsSimCalo.Hits TempCalHits RawCalo.Hits
DigiSimProcessor
SimHitsLCCollection RawHitsLCCollection
● Calorimeter hits shown here, but applies just as well to other subdetectors.
● TempCalHits are both input and output to each modifier
● All processing is controlled by a DigiSimProcessor (one per subdetector)
● Modifiers are configured at run time, via the Marlin steering file
● New modifiers can be easily created for new functionality.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Example modifiersExample modifiers
threshold
Smearedlinear
transformation
GainDiscrimination is a smearedlin.transf. + threshold on energy
SmearedLinear is a func-basedsmeared linear transformationon energy and/or timing
Einput
Eoutput
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
• Drivers needed: (all available from org.lcsim.digisim)CalHitMapDriver, DigiSimDriver and CalorimeterHitsDriver, plus LCIODriver (for standalone run, saving output file) or YourAnalysisDrivers (as an on-the-fly preprocessor)
• DigiSim configuration file stored on LCDetectors: digisim/digisim.steer
• Run it:– From command line: after setting the CLASSPATH (see
docs for details)java org.lcsim.digisim.DigiSimMain <inputfile>an output file ./digisim.slcio will be produced, to be used for analysis or reconstruction
– From inside JAS: DigiSimExample is available from Examples -> org.lcsim examples
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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The Directed Tree The Directed Tree AlgorithmAlgorithm
• Define neighborhood for a cell
• Discard cells below threshold (0.25 MIP)
• Calculate density for each cell i
• If(density==0) ?
else
calculate (Dj – Di )/dij
where j is in the neighborhood
find max []
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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The Directed Tree Algorithm (contd.)The Directed Tree Algorithm (contd.)
• If max[] is –ve
i starts a new cluster
if max[] is +ve
j is the parent of I
if max[] == 0
avoid circular loop
attach to nearest
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Single hadrons in the ECalSingle hadrons in the ECalGenerated clusters
Reconstructed clusters
Clusters from single hadrons are reconstructed well.Some “fragment”s or “satellite”s remain unassociated.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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EM clusters in ZEM clusters in Zqq Eventsqq EventsGenerated clusters
Reconstructed clusters
Only a few highest-E clusters shown.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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The confusion termThe confusion term• Internal to calorimeter.• Reconstruct “gen” and “rec” clusters,• A “gen” cluster is a collection of cells which
are attached to a particular MCparticle. All detector effects are included in this cluster.
• Find centroids and match to nearest “rec” cluster, making sure that no cluster gets associated twice.
• Somewhat conservative.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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ZZqq Eventsqq Events
• Calculate Erec/Egen for each generated cluster
• Enter into histogram with weight Egen/Etotal.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Cluster Matching and MergingCluster Matching and Merging
• Stage 1: one-to-one gen-reco matching
based on distances (3D or angular)
→ unassociated clusters (“satellites”)
• Stage 2: attach satellites to reco clusters
based on angular distances: possible cuts
on angular separation, satellite energies,
number of hits,...
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Preliminary ECal AnalysisPreliminary ECal Analysis• 500 events, with 2-
pions 10 cm apart at ECal face, using SDNPHOct04 detector
• neighborhood definition: (dφ=5, dz=5, dlayer=9)
• discard events with decays or interactions before Ecal
• Look at:– eratio1: Erec/Egen after
stage 1 (matching)
– eratio2: Erec/Egen after stage 2 (merge satellites)
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Preliminary HCal AnalysisPreliminary HCal Analysis• 500 events, with 2-pions
10cm apart at Ecal face, using SDNPHOct04 detector
• neighborhood definition: (dφ=2, dz=2, dlayer=2)
• discard events with decays or interactions before Ecal
• Look at:– eratio1: Erec/Egen after
stage 1 (matching)
– eratio2: Erec/Egen after stage 2 (merge satellites)
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Current StatusCurrent Status• Analysis of complex events shows some
problems with too many satellites – how to
associate them with the right parent shower?
• Clustering algorithm ported to org.lcsim, to be
certified. Committed to LCSim CVS repository.
• More manpower for the PFA development effort.
• Work in progress, a lot to do ...
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Current Status (contd.)Current Status (contd.)
With Perfect PFA (no confusion term), σ(E) = 3.1 GeV
Zqq
σ(E) = 4.3 GeV
•Scint, 1 cm x 1cm. •Density-weighted clustering, but analog E calculation in both ECal & HCal. •Min 5 cells for cluster. •Cell threshold = 0.5 MIP. •Satellite attachment not used.•No cut on theta.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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PlansPlans• No plans to get involved in any new simulation
development work...• Will continue to support LCDG4, but no further development• Will further develop DigiSim – a long-term product.
• ... until, perhaps, we are ready to parametrize some of the simulation (see below)
• Will concentrate more on algorithm development (with DigiSim). • New ideas on reducing the confusion term and accounting
for differences in low-E neutral hadron energy sampling need to be coded, polished.
• Enormous volumes of MC will have to be generated and analyzed to get a handle on these.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty
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Plans (contd.)Plans (contd.)• Major re-writing of code underway to make it
more object-oriented.
• Aim to be ready to analyze the TB data as soon as they become available.
• A great deal of work to do.
• Coordinated, efficient use of scarce resources is key to success.
Fermilab, 22-09-05 Simulation & PFA at NIU Dhiman Chakraborty