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 Double_t AliKFParticle::fgBz = 5.;  //* Bz compoment of the magnetic field
  28
  29 AliKFParticle::AliKFParticle( const AliExternalTrackParam &track, Int_t PID )
  30 {
  31   // Constructor from ALICE track, PID hypothesis can be provided
  32
  33   TParticlePDG* particlePDG = TDatabasePDG::Instance()->GetParticle(PID);
  34   Double_t mass = (particlePDG) ? particlePDG->Mass() :0.13957;
  35
  36   track.GetXYZ(fP);
  37   track.GetPxPyPz(fP+3);
  38   Double_t energy = TMath::Sqrt( mass*mass + fP[3]*fP[3] + fP[4]*fP[4] + fP[5]*fP[5]);
  39   fP[6] = energy;
  40   fP[7] = 0;
  41   fQ = (track.Get1Pt() >0 ) ?1 :-1;
  42   fNDF = 0;
  43   fChi2 = 0;
  44   fAtProductionVertex = 0;
  45   fIsLinearized = 0;
  46   fSFromDecay = 0;
  47
  48   Double_t energyInv = 1./energy;
  49   Double_t
  50     h0 = fP[3]*energyInv,
  51     h1 = fP[4]*energyInv,
  52     h2 = fP[5]*energyInv;
  53   track.GetCovarianceXYZPxPyPz( fC );
  54
  55   fC[21] = h0*fC[ 6] + h1*fC[10] + h2*fC[15];
  56   fC[22] = h0*fC[ 7] + h1*fC[11] + h2*fC[16];
  57   fC[23] = h0*fC[ 8] + h1*fC[12] + h2*fC[17];
  58   fC[24] = h0*fC[ 9] + h1*fC[13] + h2*fC[18];
  59   fC[25] = h0*fC[13] + h1*fC[14] + h2*fC[19];
  60   fC[26] = h0*fC[18] + h1*fC[19] + h2*fC[20];
  61   fC[27] = h0*h0*fC[ 9] + h1*h1*fC[14] + h2*h2*fC[20]
  62     + 2*(h0*h1*fC[13] + h0*h2*fC[18] + h1*h2*fC[19] );
  63   for( int i=28; i<36; i++ ) fC[i] = 0;
  64   fC[35] = 1.;
  65 }
  66
  67 AliKFParticle::AliKFParticle( const AliESDVertex &vertex )
  68 {
  69   // Constructor from ALICE vertex
  70
  71   vertex.GetXYZ( fP );
  72   vertex.GetCovMatrix( fC );
  73   fChi2 = vertex.GetChi2();
  74   fNDF = 2*vertex.GetNContributors() - 3;
  75   fQ = 0;
  76   fAtProductionVertex = 0;
  77   fIsLinearized = 0;
  78   fSFromDecay = 0;
  79 }