STAR Reconstruction Overview

1
STAR Reconstruction Overview

• S. Margetis
• Kent State University

2
Outlook

• Requirements
• environment
• Physics-based requirements
• STARs approach
• Detectors
• Year-1 vs Year-2
• Detector staging
• Reconstruction software
• Issues
• Flow chart
• Presentations at this meeting
• Day-1/2

3
Environment

• Collider - ppt ()
• Lorentz boost is weak
• Energy loss/Scattering not negligible
• dN/dy can vary but high (500-1000 charged tracks
  in central PbPb collisions)
  
• high track densities
• Physics signals differ in cross sections
• STAR concentrates mainly on hadron signals
• Typical rates of a few percent (e.g.
  strangeness)
  
• But any lepton/charm/high pt one drops
  dramatically

4
Requirements

• High overall tracking efficiency (90)
• 3-body decays/correlations
• relatively flat over p/pt with low contamination
• soft secondaries
• low/high momentum signals
• Low p/pt coverage
• TPC cutoff at 80-100MeV
• need SVT-alone tracking
• Good momentum resolution (high/low momenta)
• around 1
• Good two-track resolution
• Good (micro?) vertexing
• Good PID capabilities

5
STARs (and not only) approach

• Silicon-based tracker around the vertex region
• Excellent position/two track separation
• Can cope with expected densities of up to 10
  tracks/cm2
  
• Large TPCs for central (forward) tracking at
  larger radii
  
• about 1.5 m of tracking provides for dE/dx and
  dp/p
  
• low mass
• know-how exists

6
(No Transcript)
7
Year-1 / Year-2

• Initial (Year-1) tracking detectors
• TPC one SVT plane (ladder) FTPC
• Simpler integrated tracking tasks
• Material, trackers, matching, relative
  alignments
  
• Year-2 (2,2) configuration
• Initially SVT, then SDD
• Harder integrated tracking tasks
• Execution sequence less obvious
• DetectorGlobal handshake

8
Software

• Poor Initial Design
• Legacy code was put together and effort
  concentrated in maintenance and algorithm
  development
  
• New environment, new challenges
• Black box/Do not touch my code approach
• Different code same task
• Poor overall task integration/upgrade path
  definition
  
• Minimum (STAR dedicated) manpower/frequent infra
  changes (much better now)/lack of expertise
  
• (Part-time) physicists write/maintain code
• Co-existence of Fortran/C
• Effort started around 1992, Fortran essential
• Table based communication between modules

9
Software-2

• Good algorithmic approaches to cluster/track
  finding
  
• Based on previous experiments/experience
• Several approaches were tried out
• Basic tasks are covered even if not in an optimum
  way
  
• No huge holes in the system
• Peaceful coexistence of diverse software
• STAR will be ready to take and analyze its data
• Currently looking for common tasks/upgrade paths
• Propagation (GEANE/Kalman)
• Fitting (Kalman)
• Algorithm handshake/streamlining/integration

10
Event Reconstruction
STAR Event DAQ/GEANT
Iwona
TPC analysis
SVT analysis
FTPC analysis
Helen
Calibrations
Global
Spiros
Databases
DST
11
Presentations

• Today
• TPC software
• Response simulators
• Cluster/Hit finders
• Tracking
• Test results
• Evaluation tools
• SVT (SDDSSD) software
• Response simulators
• Cluster/Hit finders
• Tracking (stand-alone)
• Test results
• Tomorrow
• Global software
• Integrated tracking
• Matching/Fitting

12
Presentations (continued)

• Event vertex finding
• Tracking in complex non-uniform detectors
• Primary fitting
• Plans

13
Prelude, not Summary

• Listen to our choices/thinking but ask questions
• plenty of time reserved for this
• Voice your concerns or ideas on a topic