STEER/AliExternalTrackParam.cxx

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  15
  16 /* $Id$ */
  17
  18 ///////////////////////////////////////////////////////////////////////////////
  19 //                                                                           //
  20 // track parameters in "external" format                                     //
  21 //                                                                           //
  22 // The track parameters are:                                                //
  23 // - local y coordinate                                                      //
  24 // - local z coordinate                                                      //
  25 // - sin of azimutal angle                                                   //
  26 // - tan of dip angle                                                        //
  27 // - charge/pt                                                               //
  28 // The parametrisation is given at the local x coordinate fX and the         //
  29 // azimuthal angle fAlpha.                                                   //
  30 //                                                                           //
  31 // The external parametrisation can be used to exchange track parameters     //
  32 // between different detectors.                                              //
  33 //                                                                           //
  34 ///////////////////////////////////////////////////////////////////////////////
  35
  36
  37 #include "AliExternalTrackParam.h"
  38 #include "AliKalmanTrack.h"
  39
  40 ClassImp(AliExternalTrackParam)
  41
  42
  43 //_____________________________________________________________________________
  44 AliExternalTrackParam::AliExternalTrackParam()
  45 {
  46 // default constructor
  47
  48   fX = fAlpha = 0.;
  49   for (Int_t i = 0; i < 5; i++) fParam[i] = 0;
  50   for (Int_t i = 0; i < 15; i++) fCovar[i] = 0;
  51 }
  52
  53 //_____________________________________________________________________________
  54 AliExternalTrackParam::AliExternalTrackParam(Double_t x, Double_t alpha,
  55                                              const Double_t param[5],
  56                                              const Double_t covar[15])
  57 {
  58 // create external track parameters from given arguments
  59
  60   fX = x;
  61   fAlpha = alpha;
  62   for (Int_t i = 0; i < 5; i++) fParam[i] = param[i];
  63   for (Int_t i = 0; i < 15; i++) fCovar[i] = covar[i];
  64 }
  65
  66 AliExternalTrackParam::AliExternalTrackParam(const AliKalmanTrack& track)
  67 {
  68   //
  69   //
  70   track.GetExternalParameters(fX,fParam);
  71   track.GetExternalCovariance(fCovar);
  72   fAlpha = track.GetAlpha();
  73 }
  74
  75
  76 //_____________________________________________________________________________
  77 const Double_t* AliExternalTrackParam::GetParameter() const
  78 {
  79 // get a pointer to the array of track parameters
  80
  81   return fParam;
  82 }
  83
  84 //_____________________________________________________________________________
  85 const Double_t* AliExternalTrackParam::GetCovariance() const
  86 {
  87 // get a pointer to the array of the track parameter covariance matrix
  88
  89   return fCovar;
  90 }
  91
  92 //_____________________________________________________________________________
  93 AliExternalTrackParam* AliExternalTrackParam::CreateExternalParam() const
  94 {
  95 // copy this instance
  96
  97   return new AliExternalTrackParam(fX, fAlpha, fParam, fCovar);
  98 }
  99
 100 //_____________________________________________________________________________
 101 void AliExternalTrackParam::ResetCovariance(Double_t factor,
 102                                             Bool_t clearOffDiagonal)
 103 {
 104 // reset the covariance matrix ("forget" track history)
 105
 106   Int_t k = 0;
 107   for (Int_t i = 0; i < 5; i++) {
 108     for (Int_t j = 0; j < i; j++) {  // off diagonal elements
 109       if (clearOffDiagonal) {
 110         fCovar[k++] = 0;
 111       } else {
 112         fCovar[k++] *= factor;
 113       }
 114     }
 115     fCovar[k++] *= factor;     // diagonal elements
 116   }
 117 }
 118
 119
 120 //_____________________________________________________________________________
 121 Bool_t AliExternalTrackParam::PropagateTo(Double_t /*x*/, Double_t* /*length*/)
 122 {
 123 // Propagate the track parameters to the given x coordinate assuming vacuum.
 124 // If length is not NULL, the change of track length is added to it.
 125 //
 126 // NOT IMPLEMENTED for this class
 127
 128   return kFALSE;
 129 }
 130
 131 //_____________________________________________________________________________
 132 Bool_t AliExternalTrackParam::RotateTo(Double_t /*alpha*/)
 133 {
 134 // Rotate the reference axis for the parametrisation to the given angle.
 135 //
 136 // NOT IMPLEMENTED for this class
 137
 138   return kFALSE;
 139 }
 140
 141 //_____________________________________________________________________________
 142 Bool_t AliExternalTrackParam::CorrectForMaterial(Double_t /*dAngle*/,
 143                                                  Double_t /*dPrel*/)
 144 {
 145 // Take into account material effects assuming:
 146 //   dAngle2: mean multiple scattering angle in rad squared
 147 //   dPrel  : mean relative momentum gain (if > 0) or loss (if < 0)
 148 //
 149 // NOT IMPLEMENTED for this class
 150
 151   return kFALSE;
 152 }
 153
 154 //_____________________________________________________________________________
 155 Bool_t AliExternalTrackParam::GetProlongationAt(Double_t /*x*/,
 156                                                 Double_t& /*y*/,
 157                                                 Double_t& /*z*/) const
 158 {
 159 // Get the local y and z coordinates at the given x value
 160 //
 161 // NOT IMPLEMENTED for this class
 162
 163   return kFALSE;
 164 }
 165
 166 //_____________________________________________________________________________
 167 Double_t AliExternalTrackParam::GetXAtVertex(Double_t /*x*/,
 168                                              Double_t /*y*/) const
 169 {
 170 // Get the x coordinate at the given vertex (x,y)
 171 //
 172 // NOT IMPLEMENTED for this class
 173
 174   return 0;
 175 }
 176
 177
 178 //_____________________________________________________________________________
 179 Double_t AliExternalTrackParam::GetPredictedChi2(const AliCluster* /*cluster*/)
 180 {
 181 // calculate the chi2 contribution of the given cluster
 182 //
 183 // NOT IMPLEMENTED for this class
 184
 185   return -1;
 186 }
 187
 188 //_____________________________________________________________________________
 189 Bool_t AliExternalTrackParam::Update(const AliCluster* /*cluster*/)
 190 {
 191 // update the track parameters using the position and error
 192 // of the given cluster
 193 //
 194 // NOT IMPLEMENTED for this class
 195
 196   return kFALSE;
 197 }
 198
 199
 200 //_____________________________________________________________________________
 201 Double_t AliExternalTrackParam::SigmaPhi() const
 202 {
 203 // get the error of the azimuthal angle
 204
 205   return TMath::Sqrt(TMath::Abs(fCovar[5] / (1. - fParam[2]*fParam[2])));
 206 }
 207
 208 //_____________________________________________________________________________
 209 Double_t AliExternalTrackParam::SigmaTheta() const
 210 {
 211 // get the error of the polar angle
 212
 213   return TMath::Sqrt(TMath::Abs(fCovar[9])) / (1. + fParam[3]*fParam[3]);
 214 }
 215
 216 //_____________________________________________________________________________
 217 Double_t AliExternalTrackParam::SigmaPt() const
 218 {
 219 // get the error of the transversal component of the momentum
 220
 221   return TMath::Sqrt(fCovar[14]) / TMath::Abs(fParam[4]);
 222 }
 223
 224 //_____________________________________________________________________________
 225 TVector3 AliExternalTrackParam::Momentum() const
 226 {
 227 // get the momentum vector
 228
 229   Double_t phi = TMath::ASin(fParam[2]) + fAlpha;
 230   Double_t pt = 1. / TMath::Abs(fParam[4]);
 231   return TVector3(pt * TMath::Cos(phi),
 232                   pt * TMath::Sin(phi),
 233                   pt * fParam[3]);
 234 }
 235
 236 //_____________________________________________________________________________
 237 TVector3 AliExternalTrackParam::Position() const
 238 {
 239 // get the current spatial position in global coordinates
 240
 241   return TVector3(fX * TMath::Cos(fAlpha) - fParam[0] * TMath::Sin(fAlpha),
 242                   fX * TMath::Sin(fAlpha) + fParam[0] * TMath::Cos(fAlpha),
 243                   fParam[1]);
 244 }
 245
 246
 247 //_____________________________________________________________________________
 248 void AliExternalTrackParam::Print(Option_t* /*option*/) const
 249 {
 250 // print the parameters and the covariance matrix
 251
 252   printf("AliExternalTrackParam: x = %-12g  alpha = %-12g\n", fX, fAlpha);
 253   printf("  parameters: %12g %12g %12g %12g %12g\n",
 254          fParam[0], fParam[1], fParam[2], fParam[3], fParam[4]);
 255   printf("  covariance: %12g\n", fCovar[0]);
 256   printf("              %12g %12g\n", fCovar[1], fCovar[2]);
 257   printf("              %12g %12g %12g\n", fCovar[3], fCovar[4], fCovar[5]);
 258   printf("              %12g %12g %12g %12g\n",
 259          fCovar[6], fCovar[7], fCovar[8], fCovar[9]);
 260   printf("              %12g %12g %12g %12g %12g\n",
 261          fCovar[10], fCovar[11], fCovar[12], fCovar[13], fCovar[14]);
 262 }