Alice detector

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Alice detector
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Quark gluon plasmasignatures

• (Multi)Strangeness enhancement W,X,L,K
• Quarkonium suppression J/y,cc,U
• Kinematic probes pT, dN/dy,dET/dy spectra, two
  particle correlations, etc.
• Resonance shapes and positionsr,w,f
• EM probesphotons, lepton pairs
• Hyper-matter strangelets(2u2d2s,...),
  multihyperon clusters
• gt more than 10 event classes

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Alice run

• Heavy ion run 4 weeks/year (106 s)
• Hadronic physics 2x107 central events x 40Mb
  compressed raw data
• Reference minimum bias events 2x107 events x
  10Mb
• Charm and dielectron physics 2x107 events x
  2.5Mb
• Muon physics 109 events x 0.5Mb
• Proton run (107 s/year) 5x109 events x 0.2Mb

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Alice off-line project

• Initial constraints
• Huge amount of data to be processed
• Very complex detector (typical for the LHC
  experiments)
• Experiment driven physics
• Large variety of event types
• Fuzzy and changing requirements
• Need for single, modular, flexible, and reliable
  framework

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Brief history of the off-line project

• Before 1998 several independent Fortran codes
  for preparation of the Technical proposal
• Beginning of 1998 decision on a single framework
  for simulation, reconstruction, and analysis
• OO design
• Implemented in C
• Based on Root
• Interfaces to the existing Fortran code and
  smooth transition to C

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Root

• Super-PAW functionality
• Hierarchical object-oriented database
• C interpretator
• Advanced statistical analysis tool
• Optimized query mechanisms in very large data
  sets (trees)
• Rich set of container classes with I/O support
• Robust object I/O package

• Extensive set of GUI classes and visualization
  tools
• HTML documentation system
• Run-time object inspection capabilities and
  automatic schema evolution
• Client/server networking
• Remote database access
• http//root.cern.ch

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Alice off-line project AliRoot

• Rapid development 434 classes, 290K lines C
• Software framework for all activities
  simulation, digitization, monitoring,
  reconstruction, and analysis
• Opens source project available via CVS repository
• Decomposition per detector to independent modules

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A view of the offline processing
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Simulation

• Event generators
• HIJING, MEVSIM, PYTHIA for "real physics"
• HIJING parametrization for simulation of
  background events
• EventCocktail with fixed number of particles
• Hits Digits
• Geant3 stable, well known physics and
  limitations
• Geant4 new, evolving
• FLUKA excellent physics, limited geometrical and
  user's interfaces

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Alice virtual MC
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Alice background event

• 84210 particles
• Data size
• Hits 1.4Gb
• Digits 1.1Gb
• CPU time on 800MHz PIII
• Hits 24h
• Digits 15h

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Simulation strategy

• Simulation of background events
• 10 event classes x 1000 background events
• Event mixing (merging) technique
• Creation of summable digits provided for each
  detector
• Merging of signal patterns to the background
  event
• Possibility for multilayer merging
• Different storage options
• Fast parametrized MC of the response

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Simulation Ongoing activities

• Development and interface of after-burners
• Development and interface of flow generators
• Geant 4 integration hadronic tests and
  benchmarks
• TFluka interface and integration
• Radiation studies
• Improvement of the geometrical descriptions
  investigation on geometrical modellers
• Implementation of the event merging
• Refactoring of the existing code

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Reconstruction

• Exists for all detectors track segments
• Much faster than the simulation and digitization
  (TPC 30 min/central event)
• Reconstructed event size 4Mb for the data
  events, 5Mb for the simulated ones
• Software tests of the quality
• Global tracking ITSTPCTRD in progress

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Tracking requirements (ITSTPC)

• Environment
• dN/dy up to 8000 charged particle (about 4 times
  that foreseen for RHIC at BNL)
• Requirements
• good efficiency (above 90 from pT gt 0.1GeV/c )
• some efficiency also below (as low as possible)
• momentum resolution (dp/p) on the level of 1 for
  low momenta and for high momenta few at 5GeV/c
• Good secondary vertexing capability (V0, charm ?)
• particle identification capabilities, especially
  for low momentum electrons (which cannot reach
  other PID)

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TPC tracking
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dE/dx in TPC
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Reconstruction Ongoing activities

• Cluster unfolding
• Tracks from secondary vertexes
• Global Kalman track and error propagation
• Primary and secondary vertexing
• Treatment of kinks
• Fitting with constraints
• Classes for High Level Triggering
• Calibration alignment

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Analysis

• Development of AliEvent class for global
  reconstruction
• Specific classes for different signatures
• Physics Performance Report in 2002
• Detector features resolutions, efficiencies,
  etc.
• Detailed study of the possibilities to extract
  QGP signals and parameters
• Test for the production and distributed computing
  environment

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Distributed analysis project
Local
PROOF
Remote
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Organization of the Alice off-line project

• Small central team at CERN coordination,
  infrastructure, framework development, software
  tests, platforms
• Detector groups geometrical description,
  simulation, reconstruction, specific algorithms
  and tests
• Off-line board coordination, major design
  decisions, manpower planning
• Working groups on specific problems

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Alice computing structure
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Development cycle

• Rapid prototyping, rapid user's feed-back
• Micro-cycles constant update via our CVS server
• Macro-cycles major modifications, design
  choices, software releases
• Code and design reviews, refactoring

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Alice software process

• Close in spirit to the most recent software
  engineering methodology (Extreme programming,
  GNU, Open source, etc.)
• Extensive Web-based documentation updated nightly
  http//AliSoft.cern.ch/offline
• Continuous code testing (nightly builds)
• Coding conventions code analysis and reverse
  engineering tool (common project with IRST,
  Trento)

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Planning

• Based mainly on functionality milestones for
  technology and physics
• Data challenges test of the technology and
  functional integration DAQ - Off-line
• Physics challenges test of the functionality
  from the user's point of view. The Physics
  Performance Report is the first one
• Detailed planning taking into account the current
  user's requirements (lightweight use cases)
• Major release every 6 months, tags every week

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Alice data challenges milestones
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Physics challenges milestones