Java Physics Generator and Analysis Modules

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Java Physics Generator and Analysis Modules

• Mike Ronan
• LBNL
• (presented by Tony Johnson)

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Goals

• Disparate groups working worldwide on Linear
  Collider physics studies have produced
  complementary tools using a variety of languages
  and methodologies
• From a physics perspective it is desirable to
  directly compare the results from these different
  tools
• A framework for accessing different modules in a
  uniform way has been developed, allowing one
  analysis module to be used with all tools
• Methodology not specific to linear collider
  studies

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Methodology

• Use Java for building framework
• Good OO language for rapid development of
  analysis algorithms
• Use Java Native Interface (JNI) to call different
  language modules and retrieve results back into
  Java objects
• Adapt each tool to use common java interfaces
• E.g. All generators create same HEPevt
• Use existing Java analysis tools for data
  analysis
• JAS, JAIDA, etc.
• US Linear Collider physics tools (Java)
• 3,4 vector tools, jet finders, vertex finding,
  etc.
• Provide access to Java based scripting languages
• jython, pnuts, dynamic java etc.

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Event Generators Interfaced

• Pandora-Pythia V2.2 Monte Carlo using
  PanoraPythia interface package
• C and Fortran 77
• Pythia v6.2 Monte Carlo with Circe beamstrahlung
  simulation
• Fortran 77
• Whizard V1.22 Monte Carlo with ISR and Circe
  turned on
• Fortran 95

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Implementation

• Use Java native Interface (JNI)
• For interfacing to generators only need to
  implement a few methods
• setParameter() setProcess()
• init()
• generateEvent()
• getEvent() Access to HEPEvt, common to most
  generators
• finish()
• Infrastructure can be reused with little change
  between generators
• Use standard tools (gmake etc.) to build .so file
• Other libraries (i.e. CERNLIB) can be statically
  linked into .so file
• Rarely needs to be rebuilt
• All interactive work can be done in Java

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Usage Example

• Details of how to set up generator varies from
  generator to generator
• All follow same basic pattern
• All generate same set of Java objects
  representing generated particles

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More about HEPEvt classes
HEPEVT Common Block
Java Object Model HEPEvt Particle ParticleType
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Pandora, Pythia, Whizard Comparisons

• FMCParticle jet distributions
• Number of correctly reconstructed jets
• Angular distribution (Cos?Max) of jets
• Jet finder final ycut
• Direct reconstruction of Z and Higgs through
  hadronic decays.
• Good agreement between Pandora, Pythia and
  Whizard simulation

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Simulation Packages

• LCD Fast Monte Carlo v1.4 (Java)
• Charged particle momentum smearing based on
  detailed error estimates
• Gaussian energy smearing for photons and neutral
  hadrons
• Acceptance and energy threshold requirements
• Perfect energy flow
• TESLA SimDet V4.0 (Fortran 77)
• Parameterized charged and neutral energy smearing
  based on full (Brahms) Monte Carlo simulations
• Acceptance requirements
• A new energy flow algorithm
• JLC QuickSim V2.1 includes (C)
• Charged particle momentum and position smearing
  based on detailed error estimates
• Simulation of individual calorimeter cell hits
  and cluster finding
• Track-cluster association to separate charged and
  neutral clusters

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Interoperability
DetectorSimulation
Event Generators
Pythia
LCD FastMC
Pandora
Event Selection
TESLA SimDet
Analysis Code
Whizard
JLC QuickSim
Java
Fortran
C, C
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US FastMC, SimDet QuickSim Detector Simulations

• Direct reconstruction of Z and Higgs through
  hadronic decays is shown for Higgstrahlung signal
  events only. Jet-jet mass distributions for US
  FastMC, TESLA SimDet and JLC QuickSim detector
  simulations are reconstructed for
  Whizard-MadGraph Monte Carlo events including ISR
  and Circe beamstrahlung effects.
• The LCD FastMC jet-jet mass resolution is
  significantly better since it assumes perfect
  energy flow. TESLA SimDet and JLC QuickSim
  detector simulations give comparable jet energy
  resolutions but different mean reconstructed
  jet-jet masses.

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Whizzard MadGraph Higgstrahlung Event Analysis
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Conclusions and Future

• Hand coded JNI solutions works well for
  interfacing to event generators, simple
  simulation programs
• Brings advantages of Java based analysis to
  Fortran and C,C code
• Allows direct physics comparisons of disparate
  tools
• New tools are now available which will make this
  approach more scalable
• JACE http//reyelts.dyndns.org8080/jace/
• Integration with gcc-xml, or POOL dictionary?
• Web/Grid services
• LCIO Common IO system for international linear
  collider studies
• see talk by Frank Gaede at this conference)
• All tools used in this study available from
• http//www.lbl.gov/ronan/docs/lcdstudies/

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Higgstrahlung