Pixel Track Finding and Fitting

Complete: 5
Detailed Review status

Contents

Pixel Triplets and Pixel Track Fitting

The PixelTracks are simple tracks made of three (or optionally two) hits in the Silicon Pixel detector. They can be reconstructed very quickly, so are used in the HLT. The track reconstruction is done in three steps:

  • Hit Pair reconstruction (package TkHitPairs)
  • Hit Triplet reconstruction (package PixelTriplets)
  • Kinematics assignment (fitting) to hit triplet

Modules and Default config files

The module to put into your path is pixelTracks to produce the PixelTracks. Under RecoPixelVertexing/PixelTrackFitting/data you can find the base configuration files:
PixelTracks.cff and PixelTracks.cfi.

In RecoPixelVertexing/PixelTrackFitting/test/test.cfg you will see an example of how to put these in your path.

Tutorial Instructions

In the src directory of your CMSSW area checkout the RecoPixelVertexing validation test package:
cvs checkout  Validation/RecoPixelVertexing/test
cd Validation/RecoPixelVertexing/test
scramv1 b
cmsRun tutorial-Track.cfg
With the last command you run cmssw with the tutorial-Track.cfg configuration file. From reconstruted pixel hits it creates triplets and a 3-hits tracks. Track by track the reconstructed kinematics is dumped on screen. After that the simple analysis that compare generated and reconstructed tracks is done. The analysing module is in PixelTrackVal.cc. There you may find the code needed to access reconstructed tracks:
  edm::Handle<reco::TrackCollection> trackCollection;
  std::string trackCollName = conf_.getParameter<std::string>("TrackCollection");  
  ev.getByLabel(trackCollName, trackCollection);
  const reco::TrackCollection tracks = *(trackCollection.product());
The histograms created by analysis programm appear in pixelTrackHistos_Tut.root file. One can create a test plots by executing a command
root -b -p -q DoCompare.C\(\"pixelTrackHistos_Tut\"\)
In the output pixelTrackHistos_Tut_0.eps file one can see 6 plots. pixelTrackHistos_Tut_0.jpg

  • h_Pt (top-left): distribution of (pt_gen - pt_rec)/pt_gen
  • h_dR (top-middle): distribution of Delta R (ie. sqrt( sqr(Delta phi)+sqr(Delta eta)) ) between simulated and reconstructed track
  • h_TIP (top-right): distribution of reconstructed impact parameter
  • h_VtxZ (bottom-left): difference between simulated track z coordinate of vertex and z-coordinate of point of closest approach to beam line
  • h_VtxZ_Pull (bottom-middle): |z_rec-z_gen|/sigma_z, ie. pull reconstructd z (as before)
  • h_Nan (bottom-right): for debug onle - illegal values (Nan's) in track parameters.

Review status

Reviewer/Editor and Date (copy from screen) Comments
Main.JennyWilliams - 05 Dec 2006 tidied, added completeness bar, responsible/review fields.

Responsible: MarcinKonecki
Last reviewed by: MarcinKonecki - 04 Dec 2006

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Topic revision: r31 - 2008-02-18 - MarcinKonecki
 
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