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Physics and Detector Simulations
Norman Graf
June 13, 2000
Common GoalsProvide full simulation of Linear Collider
physics program:Physics simulationsDetector simulationsReconstruction and analysis
Need flexibility for:New detector geometries/technologies Different reconstruction algorithms
Limited resources demand efficient solution, focused effort.
LCD Software Road Map
stdHEP files
fastMC (JAS)
JAS analysis
ASCII raw data
Gismo
Full Recon
Root parser
JAS parser
.lcd filesRoot files
Gismo Material FilesGenerator FilesTrack Momentum Resolution Tables
Parameter Files (JAS)Geometry Description FilesParameter Files (Root)
fastMC (Root)
ASCII recon
Root files
.lcd files
Root Analysis
JAS parser Root parser
Generator(s)
Full SimulationsDetailed descriptions of the detector
elements, complete accounting of physics processes, track swimming, particle showering, etc. Essential for detector development and derivation of fast simulation parameterizations.
GISMO GEANT4
Fast Simulations Simulations based on parameterized,
or simplified detector responsesFast, can be flexible, but limited.
ROOT JAVA
Future Plans
Fully document existing tools.Implement and validate fast simulations:
Full covariance matrix for tracksCalorimeter parameterizations
Improve reconstruction for full simulationtrack finding/fittingcalorimeter clustering
Reconstruction
Default jet findingParticle IDImplement vertex finding/fitting
Develop event data model and implement persistence for reconstructed events.
Undertake physics studies.
ConclusionsBoth full and fast simulation programs exist
S2 and L2 close to production.
Need feedback from detector and physics groupsWhat do you need? When do you need it?
Simulations in a state of flux, input requested.GISMOGEANT4JAS + ROOT fast simulations?
Welcome a wider collaboration on simulation efforts.
Gismo: Full SimulationReasonably full-featured full simulation package - C++
complex geometriesEGS & GHEISHA
cutoffs set at 1 MeVmultiple scattering, dE/dx, etc
Generator input from /HEPEVT/ via FNAL STDHEP I/O packageDigitization
trackinghit points at tracking/VXD layers
calorimeterstotal energy per channel
muon stripsall digi’s have full MC record
Output to ascii file
allows parsers to translate to JAS & Root for further analysis/processing e+e- -~~
Full Sim: Geometry Elements
Most detector types are cylindersinput by ascii detector filetrackers and calorimeters can have
inner/outer skins and endplatestracker/VXD layers can be
individually positioned and sizeduser sets longitudinal cell
composition (multi-materials allowed) and ‘sensitivity’
conical masks configurable
B=3TB=6T
Small Detector
3 Tracker Doublets1.1 mm G10, 600 m Sir = 14, 42, 71 cmouter layers extend to z=149 cm
5 EC Tracker disksz = 31, 61, 91, 121, 149 cminner r follows cos =0.99
Luminosity monitor (Si/W)active from 30-116 mrad
‘Vestigial’ maskcone from r=1.2 cm at z=10 cm to r=20cm at z=155 cm
Coil: 23 cm Al - between EM & HAD cals!
CalorimetryHAD cal: 2 cm Cu; 0.5 cm scintEM cal: 0.2 cm W; 0.03 cm Si
Large Detector144 Layer TPC
r = 25-200 cmlength = 5.8 m4.5 cm Al endplates0.18 cm Al inner/outer skins
Luminosity monitor (Si/W)active from 16-83 mrad
‘Vestigial’ maskcone from r=1.2 cm at z=10 cm to r= 25 cm at z=300 cm
Coil: 40 cm Al - between HAD and MU cals
CalorimetryHAD cal: 0.8 cm Pb; 0.2 cm scintEM cal: 0.4 cm Pb; 0.1 cm scint
Recent Improvements
Detector Descriptions now in XML (J.Bogart)More control over detector configurationEasier to change detector configuration
S1, L1 detectors converted to XML
Refinement of detectors as agreed at SLAC workshop:• Improved end-cap tracking• Finer calorimeter segmentation, theta segmentation
L2 – ready to go (except instrumented masks)S2 – being prepared by Ron Cassell
XML files are available for checking:• http://www.slac.stanford.edu/~jrb/nlc_detectors/
Many Bug fixes
Moving from ASCII to SIO File format
Beam Background Overlays (Gary Bower)
Take output from Guinea Pig beam simulation (from IR/backgrounds group)
Feed into full Gismo simulationBuild library of simulated background
bunchesOverlay backgrounds on signal events at
start of reconstructionAdjust timing of hits (for TPC e.g.)Add energy in calorimeter cells
Allows to change #bunches/train, bunch timing
JAS Physics UtilitiesPhysics Utilities
4-vector, 3-vector classesEvent shape/Thrust finderJet Finders
Many kT algorithms implemented (e.g. Jade and Durham )Extensible to allow implementation of other algorithms
Contributed AreaAnalysis Utilities and sample analyses provided by
users
2 Event Displays2D - Suitable for debugging reconstruction and
analysisWired for full 3D support
Particle Hierarchy Display
2D Event Display
Wired (M. Donszelmann – CERN)
Physics GeneratorsThere have been recent updates to
Pandora.A general purpose framework which allows
polarization and initial-state interactions to be simulated.
The Pandora-Pythia interface exists.Any generator producing STDHEP-format
output can be used as input to simulationsPYTHIA, ISAJET, etc.
Tracking ReconstructionHit Smearing/Efficiency (since Gismo gives “perfect”
hits)Random Background overlayTrack Finding:
uses M.Ronan’s (TPC) pattern finding Tuned for Large + Small detector
Track Fitters:SLD Weight Matrix FitterCan do Single Detector or Combined fit (e.g. VTX+TPC)
What’s still needed:More Track Finding Algorithms (Cheater, Projective Geometry)End Cap tracking, Hit MergingKalman Filter (incorporating multiple scattering)
Calorimeter ReconstructionCluster Finding
Three Clustering Algorithms Currently ImplementedCluster Cheater (uses MC truth to “cheat”)Simple Cluster Builder (Touching Cells)Radial Cluster Builder
• All algorithms tend to produce many very low energy clusters - important to set sensible thresholds
Still Needed - Cluster Refinement StageCombine HAD + EM clustersEndcap + Barrel overlap region
In Progress - Track Cluster AssociationInitial Implementation Done by Mike RonanOutput Format defined by Gary BowerNeed to Extend Definition of Clusters
Directionality, Entry point to calorimeter
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