STEER/AliKFParticle.cxx

   1 //----------------------------------------------------------------------------
   2 // Implementation of the AliKFParticle class
   3 // .
   4 // @author  S.Gorbunov, I.Kisel
   5 // @version 1.0
   6 // @since   13.05.07
   7 //
   8 // Class to reconstruct and store the decayed particle parameters.
   9 // The method is described in CBM-SOFT note 2007-003,
  10 // ``Reconstruction of decayed particles based on the Kalman filter'',
  11 // http://www.gsi.de/documents/DOC-2007-May-14-1.pdf
  12 //
  13 // This class is ALICE interface to general mathematics in AliKFParticleCore
  14 //
  15 //  -= Copyright &copy ALICE HLT Group =-
  16 //____________________________________________________________________________
  17
  18
  19 #include "AliKFParticle.h"
  20 #include "TDatabasePDG.h"
  21 #include "TParticlePDG.h"
  22 #include "AliExternalTrackParam.h"
  23 //#include "TMath.h"
  24
  25 ClassImp(AliKFParticle)
  26
  27
  28   AliKFParticle::AliKFParticle( const AliExternalTrackParam &track, Double_t bz, Int_t PID ) : fBz(bz)
  29 {
  30   // Constructor from ALICE track, PID hypothesis can be provided
  31
  32   TParticlePDG* particlePDG = TDatabasePDG::Instance()->GetParticle(PID);
  33   Double_t mass = (particlePDG) ? particlePDG->Mass() :0.13957;
  34
  35   track.GetXYZ(fP);
  36   track.GetPxPyPz(fP+3);
  37   Double_t energy = TMath::Sqrt( mass*mass + fP[3]*fP[3] + fP[4]*fP[4] + fP[5]*fP[5]);
  38   fP[6] = energy;
  39   fP[7] = 0;
  40   fQ = (track.Get1Pt() >0 ) ?1 :-1;
  41   fNDF = 0;
  42   fChi2 = 0;
  43   fAtProductionVertex = 0;
  44   fIsLinearized = 0;
  45   fSFromDecay = 0;
  46
  47   Double_t energyInv = 1./energy;
  48   Double_t
  49     h0 = fP[3]*energyInv,
  50     h1 = fP[4]*energyInv,
  51     h2 = fP[5]*energyInv;
  52   track.GetCovarianceXYZPxPyPz( fC );
  53
  54   fC[21] = h0*fC[ 6] + h1*fC[10] + h2*fC[15];
  55   fC[22] = h0*fC[ 7] + h1*fC[11] + h2*fC[16];
  56   fC[23] = h0*fC[ 8] + h1*fC[12] + h2*fC[17];
  57   fC[24] = h0*fC[ 9] + h1*fC[13] + h2*fC[18];
  58   fC[25] = h0*fC[13] + h1*fC[14] + h2*fC[19];
  59   fC[26] = h0*fC[18] + h1*fC[19] + h2*fC[20];
  60   fC[27] = h0*h0*fC[ 9] + h1*h1*fC[14] + h2*h2*fC[20]
  61     + 2*(h0*h1*fC[13] + h0*h2*fC[18] + h1*h2*fC[19] );
  62   for( int i=28; i<36; i++ ) fC[i] = 0;
  63   fC[35] = 1.;
  64 }
  65
  66 AliKFParticle::AliKFParticle( const AliESDVertex &vertex, Double_t bz): fBz(bz)
  67 {
  68   // Constructor from ALICE vertex
  69
  70   vertex.GetXYZ( fP );
  71   vertex.GetCovMatrix( fC );
  72   fChi2 = vertex.GetChi2();
  73   fNDF = 2*vertex.GetNContributors() - 3;
  74   fQ = 0;
  75   fAtProductionVertex = 0;
  76   fIsLinearized = 0;
  77   fSFromDecay = 0;
  78 }