Atlas software developments

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Atlas software developments

• Stan Bentvelsen

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Layout

• Atlas software status
• Milestones
• Frameworks
• Building simulation
• Geant4 validation
• Detector Description
• Reconstruction
• Event definition
• Track reconstruction
• Preparations for physics
• Analysis plans

Preparations, preparations
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Timeline towards start LHC
2005
2006
2004
2003
2002
2001
04 Simulation Geant4 validation 06 Major
migration to OO software (no Fortran!) 12 Core
software agreements complete 12 Data Challence
0 (continuity check)
06 Physics readiness report 07 Full chain
real environment 12 Full database infrastructure
04 DC1 (large scale reconstruction
analysis) 08 Computing TDR finished 12 10
processing farm 12 100 TB dBase prototype
01 40 processing farm 06 LHC beam tunes
04 - LHC pilot run 06 - 100 processing farm 08
LHC fist physics run
06 Decide OS (linux?) 07 DC2 (increased
complexity)
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Framework in Atlas
schism
Development of the C core software

• Reconstruction/analysis
• Athena
• Gaudi Framework from LHCb
• Developed further by American groups (LBL)
• Keywords
• Event store on which algorithms and services act
• Transient/persistency split
• Thoughtful design

• Simulation
• FADS/Goofy
• Based on Geant 4 event loop
• Developed by European / Japanese collaborators
• Keywords
• Extremely lightweight
• Efficient
• Little default behavior

Geant4 based Object Oriented Folly
Objectivity / ASCII
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Geant 4 physics validation

• Major milestone in ATLAS Simulation.
• The goal of the validation is to increase trust
  in Geant4 simulation (as much as G3) such that it
  can be used for data production.
• Collaboration projects with the Geant4 team.
• ATLAS own internal activity.
• Status of Geant4 similar to status of Geant3
  before LEP started (around 85)
• Geometry workable (one annoying bug)
• Electromagnetic physics fine (upto level)
• Hadronic physics less well described

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Muon Detector

• EM shower production by muons in absorber extra
  hits in Muon Drift Tubes
• Transverse distance of extra hits from muon
  track in Geant-4 broadly reproduces test beam
  data
• Detailed agreement better for lighter absorber
  material

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Tile Calorimeter
G4
G3
Geant3 vs data
data
100 GeV
Geant4 vs data
20 GeV
Electrons
Muons

• No perfect match between G4 and test beam data

8
FADS/Goofy robustness test

• Geant4 simulation test (done before Xmas01)
• 100 job-streams each of which processes 1,000
  events

Objectivity Database
Objectivity Database
Hits/ Hit-collections MCTruth
FADS/Goofy
Stream 001
HepMC
H-gt 4 leptons
1,000 events
Hits/ Hit-collections MCTruth
FADS/Goofy
Stream 002
HepMC
Pythia 6
1,000 events
FADS/Goofy
Hits/ Hit-collections MCTruth
Stream 100
HepMC
1,000 events
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FADS/Goofy robustness test

• Expected data size and CPU required
• per event 1,000 events
• 4-vectors database 50 KB 50 MB
• Hits/Hit-collections 1.5 MB 1.5
  GB database
• CPU 60 sec 17 hours (Pentium III,
  800MHz)
• Required resources
• PC farm 10 CPUs ( 5 machines with dual
  processors)
• Disk space 155 GB
• Process period 1 week

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Detector description scope
Geometry description Materials Identifiers Con
ditional dBase Alignment
Simulation Fast simulation Digitalization Visua
lization Reconstruction
provider
client
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DD of ideal static detector

• Define geometry description for ATLAS in ascii
  format
• Use XML
• Unambiguous storage of numbers with their meaning
• Customized syntax
• Many free software tools
• Parsing, validating
• Widely accepted standard
• AGDD syntax
• Geometry dBase
• Logical description (Identifier)
• Material dBase

• E.g. geometry dBase contains
• Volumes
• Generic and descriptive
• Elementary solids
• Boolean solids
• Logical groupings of volumes
• Iteration
• Positioners
• Description of the instances of the volumes
• Absolute or relative, single or multiple
• Define the translation and rotation matrix wrt
  origin of the constituents
• Utilize symmetries

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Example XML implementation
AGDD Header, version of DTD
Section sub-detector author version
Section detector, version, author
Creation solid tube
Various positioning of volumes
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AGDD parametric description

• Problem with explicit description
• Many redundant numbers
• Allow for parametric description

• Compactification
• Specialized XML syntax
• Contain parameters as attributes
• Associated C algorithms to unpack
• Registration of algorithms to create transient
  objects

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The Geant4 client

• Build the Geant4 geometry from the information
  stored in XML

• Generic translation
• Automatic translation blind to the specific
  detector
• Need explicit description
• G4Builder
• Detector specific translation
• Need algorithmic (compact) description
• Close connection to ATLAS simulation group

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SCT gallery
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Muon gallery
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Status AGDD in ATLAS
Work ongoing to create AGDD interface for all
sub-detectors in ATLAS. To agree among large
community of people is not trivial!
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• Simulation of the cosmic ray setup (at NIKHEF)
• Franks description of the geometry

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Cosmic ray material-budget
All materials
Aluminum
MDT tubes

• Standard tool (in G4Builder)
• 3d scan in (eta-phi) of geantinos
• Connection hits to digits available

Radiation length
Volume counter
deg
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Digitization
D Calvet

• Common frame for SCT and PIXEL
• From hits to digits
• Surface charge
• Charged diodes
• Digits
• Detector element
• Local description of
• SCT strips
• Pixel diodes
• Modular design
• Plug-in parameterizations
• Detailed versus fast simulation

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Silicon wafer local description
A Fornainii

• Strips/pixels will not be separate volumes in G4
• Separate packages describing readout structure
• segmentation into diodes
• connection to readout electronics

Pixel module
Barrel strip module
Endcap strip module
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Event model

• Collection of digits
• Each collection connected to one detector
  element
• Each digit connected to one readout channel
• Detector-element description from XML

• Comparison to test beam data
• Threshold scan well described by the simulation

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Track reconstruction

• AMBER first full OO tracking algorithm (P.
  Hendriks, 2000)
• COBRA COmBined Reconstruction (W. Lavrijsen)
• Global generic track fitting using
• Track segment refit inner tracker and muon
  chambers
• Extrapolation and matching from track segments
• Global track refit

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COBRA comparison

• COBRA performs well

• Comparable results for IPATREC
• (inner tracker)
• Comparable results for MUONBOX
• (muon detector)

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Higgs reconstruction
Golden channel at MHlt400 GeV benefit from
combined reconstruction
inner
muon
comb ()
130 GeV 1.57 2.55 1.18
170 GeV 1.50 2.36 1.35
200 GeV 1.78 2.45 1.61
400 GeV 20.6 21.8 20.2
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ATLAS physics at NIKHEF

• Main themes of interest have been defined
• Higgs, SUSY, Top, B-physics
• NIKHEF staff will become active players in these
  fields
• Develop NIKHEF toolkit, eg track reconstruction,
  jet definitions, front-end analysis.
• PhD students
• Higgs -gt 4 leptons (Lavrijsen, Peters, Woudstra)
• SUSY (Buis)
• Observation of Bc, production model (Scholte)
• Bs mixing, CP violation (Fornaini)
• Single top with polarization, Vtb and mass
  (Barisonzi)
• Students in the group
• G. Lim, Y. Boer, F Jansen, B Dirks, J Dalhuizen

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Conclusions

• Big challenge to get the Atlas software ready at
  startup of LHC
• Middle of development
• Transition to OO software paradigm
• Detector description going
• Geant4 toolkit validated. Atlas simulation
  underway.
• Reconstruction/analysis chain getting up steam