Declaration :

TPhTrackFinder *tf = new TPhTrackFinder(); // if you put an integer argument, you'll have some welcome message.

Event by event setting:

There are two important inputs: Primary vertex position and Front-end tracking information. Once you set the vertex position, Track Finder will pick-up the Hough Table relevant to the position automatically in the directory $HOUGH. Frond-end tracking information is necessary for this version of Hough PR, but I think I can also provide a Hough-PR version without the information.

tf->SetVertex(float x,float y,float z) ; // this function should be called for each event in order to read correct Hough Table

tf->SetSeedList(TObjArray *seedlist); // set the track seed list (output of  TPhTrackSeedFinder )

Setting parameters:

There are two important parameters which have to be chosen by user: Sigma of QP variance when chaining two match-sticks and Sigma of theta. I recommend you to set these two variables carefully and  meaningful, like 3 sigma, in order not to loose real tracks in the generation of the track candidates. More candidates means more CPU time to select  real tracks but it guarantee a better efficiency.

tf->SetErrorQP(int pair,float sgm_qp); // allowed qp variation when chaining Hough Match-Sticks for the i'th pair

tf->SetErrorTH(int pair,float sgm_th); // allowed th variation when chaining Hough Match-Stick for the i'th pair

There are two paramters which are introduced because of the error on the direction of a track seed. I believe that these parameters should be determined in the TrackSeedFinder and be set there. So I hope that these parameters become obsolete sonner or later.

tf->SetErrorTheta(float sgm_theta); // error on theta of a seed (will be determined in TrackSeedFinder soon)

tf->SetErrorPhi(float sgm_phi); // error on phi of a seed (will be determined in TrackSeedFinder soon)
 

Remarks:

1) At this moment, Hough-PR works only for the nominal vertex, 0,0,0.
2) TrackSeedFinder should be run before TrackFinder.

Example macros

{
  //
  // data file
  //

  TPhDST data("$PHATHOME/macros/tracking/sample_event.root");
  gSystem->Setenv("HOUGH","/home/icpark/hough_tables/"); // put your own hough table directory

  //
  // detector
  //

  TPhDetector *det = TPhDetector::GetInstance();
  if (!det)    det=data.GetDetector();

  //
  // Installation of PHOBOS reconstruction package & tools
  //

  TPhTrackSeedFinder *tsf   = new TPhTrackSeedFinder(1);
  TPhTrackFinder     *tf    = new TPhTrackFinder(1);

  //
  // Event loop
  //

  TPhEvent *event;
  while (event=data->GetNextEvent() )
  {

    // event initialization

    event->Print();
    det->SetEvent(event);
    det->FillWithEventHits("PMCHits");

    // Do Front-end Tracking

    tsf->RunMulguisin(1); //no argument means no message
    TObjArray *seeds = tsf->GetTrackSeedList();

    // Set event-by-event parameter

    tf->SetVertex(0,0,0); // works only for 0,0,0, at the moment
    tf->SetSeedList(seeds);

    // Run the actual Hough-PR

    tf->RunHough(1); // no argument means no message

    // Access the output

    TObjArray *candidates=tf->GetTrackList();
    int n_candidates=candidates->GetEntries();

    // terminate an event

    det->DeleteHits();
    delete event;
  }
}