Linear Collider Simulation Tools

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Linear Collider Simulation Tools

Norman Graf ACFA LC Workshop Taipei, Nov. 8, 2004
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Detector Requirements

• Detectors designed to exploit the physics
  discovery potential of ee- collisions at ?s
  1TeV.
• Will perform precision measurements of complex
  final states.
• Require
• Exceptional momentum resolution
• Excellent vertexing capabilities
• Energy Flow calorimetry
• Hermeticity

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Detector Requirements

• Yes, but still need to quantify!
• Exceptional momentum resolution
• is dp/p few 10-5 really necessary!
• How important is material?
• Excellent vertexing capabilities
• What are the effects of inner radius, thickness,
  number of layers
• Energy Flow calorimetry
• Is 30/?E needed? Can we do better?

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Particle Flow Motivation

• Measure momenta of charged tracks in the tracker
  with superb resolution.
• Measure photons in highly segmented EM
  calorimeter with reasonable resolution.
• Remaining neutral hadrons measured in hadron
  calorimeter.

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No tool is too simple
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Tracker Resolution Tool lcdtrk

• Bruce Schumm has developed a nice tool which
  allows rapid investigation of tracker designs.
• Input is simplified geometry, materials and point
  resolution.
• Output is resolution plots plus covariance
  matrices which can immediately be used to smear
  tracks in the fast Monte Carlo.
• http//www.slac.stanford.edu/schumm/lcdtrk.tar.gz
  

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Fast MC

• Covariantly smears charged tracks.
• Smears neutral calorimeter showers by expected
  resolutions.
• Can be used as input for further analyses.
• Jet Finding
• ZVTop vertexing
• Can vary resolutions at analysis time and produce
  plots of x vs resolution, eff., etc.

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LC Detector Full Simulation
GEANT4
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LCD Full Simulation

• Geometry defined in XML.
• Flexible, but simplified volumes.
• Projective readout of sensitive volumes.
• Dynamic topology, not just parameters.
• Have defined generic hit classes for sensitive
  tracker and calorimeter hits.
• LCIO bindings for I/O.

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LC Detector Simulations

• Use simplified volumes to investigate larger
  number of designs, allowing dynamic topologies
  using single executable.
• Describe optimal detector in detail.

TPC Tracker, Si Disks, CCD VTX
All Si Tracker, CCD VTX
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Reconstruction/Analysis Overview

• Java based reconstruction and analysis package
• Runs standalone or inside Java Analysis Studio
  (JAS)
• Fast MC
• Smeared tracks and calorimetry clusters
• Full Reconstruction
• track finding and fitting
• calorimeter clustering
• Individual Particle reconstruction (cluster-track
  association)
• Analysis Tools (including WIRED event display)
• Physics Tools (Vertex Finding, Jet Finding,
  Flavor Tagging)
• Beam Background Overlays

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hep.lcd Physics Utilities

• Physics Utilities
• 4-vector, 3-vector classes
• Event shape/Thrust finder
• Jet Finders
• Many kT algorithms implemented (e.g. Jade and
  Durham )
• Extensible to allow implementation of other
  algorithms
• Event Display
• Topological Vertexing
• Implementation of SLDs ZVTOP
• Event Generators
• Can be run directly in FastMC
• Can be run standalone, e.g. for writing stdhep
  files
• Diagnostic Generator
• User-defined particle mix, momenta and vertices.
• Generator framework extensible for other
  generators
• PYTHIA, HERWIG, ISAJET,

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hep.lcd analysis tools

• Tutorial http//jas.freehep.org/jas3/Tutorial/ind
  ex.html

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WIRED Event Display
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Reconstruction Status

• Full Reconstruction package which incorporates
  all aspects of the Particle Flow paradigm, works
  for any detector, and works out-of-the box is not
  currently available.
• However, many of the pieces are in place, can be
  used today, active work is underway to
  incorporate into a finished product.
• Aim to release full package prior to LCWS05 and
  use for studies at Snowmass CDR.

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Testing Samples

• Testing reconstruction on simple events. Study
  finding efficiency, fake rates and measurement
  resolutions (E, p, mass) using
• Single Fundamental Particles
• e/-, ?, ?/-, ?/-
• Simple Composite Single Particles
• ?0, ?, ?, ?, ?
• Complex Composite Single particles
• Z, W
• Physics Events

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Conclusions

• A fairly complete suite of simulation tools
  exists for LC physics and detector studies.
• Contributions to the full reconstruction welcomed
  and invited, but much can be done within the
  existing framework with released software.

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Most important tool of all!
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Links

• LC Simulations http//lcsim.org
• JAS3 http//jas.freehep.org/jas3
• WIRED http//wired.freehep.org/
• Discussion Forums
• http//forum.linearcollider.org