STAR Software Walk-Through

1
STAR Software Walk-Through
2
Doing analysis in a large collaboration Overview

• The experiment
• Collider runs for many weeks every year.
• A lot of data to look at!
• In 2007, 70M minimum bias events.
• Need computers to be able to analyze vast
  dataset.
• Analysis Software
• Find relevant data
• Develop analysis code
• Interface to the data
• Analysis code plots and correlations of
  experimentally measured quantities
• Submitting jobs to the batch farm
• Plotting results

3
Computing resources

• Facilities available for STAR
• PDSF (in Berkeley, part of NERSC)
• Parallel Distributed Systems Facility
• RCF (in Brookhaven Lab)
• RHIC Computing Facility
• Log in to PDSF pdsf.nersc.gov
• Web page
• http//www.nersc.gov/nusers/resources/PDSF/
• FAQ
• USER accounts
• Monitoring of farm conditions
• Log in to RCF rssh.rhic.bnl.gov
• Web page
• http//www.rhic.bnl.gov/RCF/

4
Doing Analysis 101

• For real or simulated data that has already been
  produced into a standard format

Run analysis on data. Tools MuDST StMcEvent
Plot results of analysis. Tools ROOT classes.
Find Data HPSS NFS local. Tools FileCatalog
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Tools

• FileCatalog (get_file_list.pl)
• http//www.star.bnl.gov/STAR/comp/sofi/FileCatalog
  /
• Finding Files (of course) that satisfy certain
  conditions
• production library used, trigger setup used, run
  numbers, collision system,
• i.e. it is a database of our data.
• Examples of usage found in link above.
• Note for PDSF make sure you have a .chos file.
  I selected /auto/redhat8 as my environment.
• Without an environment properly set, perl wont
  work!

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Tools

• Scheduler
• Used to submit jobs to the RCAS linux farm in
  batch mode.
• RCAS 10 interactive nodes, 150 batch nodes.
• How to use it
• XML script that specifies
• files to be used (e.g. using a catalog query)
• macro to be executed (i.e. analysis to be done)
• what to do with the output

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Analyzing Example Real Data, Step I

• Find events of interest
• e.g. Au Au collisions, 200 GeV. (2004 data)
• Many collisions and triggers have been used.
• Example Looking at Minimum bias triggers
• This trigger is meant to capture almost all
  interactions.
• Every trigger detector introduces a bias, this
  trigger is meant to reduce the bias introduced as
  much as possible.
• Trigger ID
• Each file can have events that were selected by
  various trigger conditions
• ID picks out a given trigger condition.
• 2004 list of triggers
• http//www.star.bnl.gov/protected/common/common200
  4/trigger2004/triggers2004.html

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A file catalog query

• pc2606 54gt get_file_list.pl -keys
  'path,filename' -cond 'storageNFS,filenamest_phy
  sics,collisionauau200,filetypedaq_reco_mudst'
  -limit 10
• /dante3/starprod/reco/productionCentral/FullField/
  P02ge/2001/321st_physics_2321030_raw_0102.MuDst.
  root
• /dante3/starprod/reco/productionCentral/FullField/
  P02ge/2001/321st_physics_2321003_raw_0127.MuDst.
  root
• /eliza12/starprod/reco/productionMinBias/FullField
  /P05ic/2004/030st_physics_5030114_raw_1010013.Mu
  Dst.root
• /eliza12/starprod/reco/productionMinBias/FullField
  /P05ic/2004/030st_physics_5030114_raw_1010022.Mu
  Dst.root
• /eliza12/starprod/reco/productionMinBias/FullField
  /P05ic/2004/030st_physics_5030114_raw_1020018.Mu
  Dst.root

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Define an Analysis Task

• Examples
• Multiplicity Distribution
• Probability to find events with Nch tracks.
• Nch number of charged particles in the event
  (typically, per unit rapidity at midrapidity).
• pT distribution of charged tracks for all events.
• Probability to find a track with a given pT.

10
The Maker framework

• Makers are a way to standardize the way we do
  analysis
• All have to prepare or initialize
• e.g. book histograms and trees
• All do something every event
• e.g. calculate or obtain distributions of
  interest
• All have to clean up when the job is done
• e.g. write the histograms

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Example Maker code

• In PDSF
• /auto/pdsfdv39/starspec/pdsfdv34/starspec/calderon
  /tutorials/StRoot/StMuDstExampleAnalysisMaker
• All Makers live under a directory called StRoot
• Compilation of the analysis code is done in same
  directory where StRoot directory (or link) is
  found
• cons StMuDstExample
• Running is done in same directory where
  compilation was done. Example in
  StRoot/macros/examples/
• root4star b q RunMuDstExample.C(500)'

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Plotting the results

• Open the output file (dummyFile00.root) in root.
  Can issue C commands on the root classes
  interactively.
• Set a sensible color scheme
• gStyle-gtSetPalette(1,0)
• Create canvases (TCanvas)
• TCanvas cnv1 new TCanvas(cnv1,multiplicity,
  600,600)
• For drawing histograms
• TH1Draw()
• mMult-gtDraw()
• Can change line color, width, style
• mMult-gtSetLineColor(2)
• mMult-gtSetLineWidth(3)
• mMult-gtSetLineStyle(11)
• Can draw markers
• mMult-gtSetMarkerStyle(20)
• mMult-gtDraw(P)
• For reproducibility, can also put all the
  commands into a macro, and just execute the
  macro
• .x plotMultExample.C

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Analyzing Example Simulation, Step I

• Generate events of interest
• e.g. Lambda_c, Upsilon, J/Psi particles according
  to a distribution
• e.g. use event generators
• PYTHIA
• HERWIG
• HIJING
• NEXUS
• AMPT
• MPC
• For large datasets, request is done officially to
  STAR simulation (Maxim Potekhin, simulation
  leader)