STEER/AliExternalTrackParam.cxx

   1 /**************************************************************************
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   3  *                                                                        *
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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 #include <TMath.h>
  37 #include <TVector3.h>
  38
  39 #include "AliExternalTrackParam.h"
  40 #include "AliKalmanTrack.h"
  41
  42 ClassImp(AliExternalTrackParam)
  43
  44
  45 //_____________________________________________________________________________
  46 AliExternalTrackParam::AliExternalTrackParam() :
  47   AliTrackParam(),
  48   fX(0),
  49   fAlpha(0)
  50 {
  51   //
  52   // default constructor
  53   //
  54   for (Int_t i = 0; i < 5; i++) fParam[i] = 0;
  55   for (Int_t i = 0; i < 15; i++) fCovar[i] = 0;
  56 }
  57
  58 //_____________________________________________________________________________
  59 AliExternalTrackParam::AliExternalTrackParam(Double_t x, Double_t alpha,
  60                                              const Double_t param[5],
  61                                              const Double_t covar[15]) :
  62   AliTrackParam(),
  63   fX(x),
  64   fAlpha(alpha)
  65 {
  66   //
  67   // create external track parameters from given arguments
  68   //
  69   for (Int_t i = 0; i < 5; i++) fParam[i] = param[i];
  70   for (Int_t i = 0; i < 15; i++) fCovar[i] = covar[i];
  71 }
  72
  73 //_____________________________________________________________________________
  74 AliExternalTrackParam::AliExternalTrackParam(const AliKalmanTrack& track) :
  75   fX(0),
  76   fAlpha(track.GetAlpha())
  77 {
  78   //
  79   //
  80   track.GetExternalParameters(fX,fParam);
  81   track.GetExternalCovariance(fCovar);
  82 }
  83
  84 //_____________________________________________________________________________
  85 const Double_t* AliExternalTrackParam::GetParameter() const
  86 {
  87 // get a pointer to the array of track parameters
  88
  89   return fParam;
  90 }
  91
  92 //_____________________________________________________________________________
  93 const Double_t* AliExternalTrackParam::GetCovariance() const
  94 {
  95 // get a pointer to the array of the track parameter covariance matrix
  96
  97   return fCovar;
  98 }
  99
 100 //_____________________________________________________________________________
 101 AliExternalTrackParam* AliExternalTrackParam::CreateExternalParam() const
 102 {
 103 // copy this instance
 104
 105   return new AliExternalTrackParam(fX, fAlpha, fParam, fCovar);
 106 }
 107
 108 //_____________________________________________________________________________
 109 void AliExternalTrackParam::ResetCovariance(Double_t factor,
 110                                             Bool_t clearOffDiagonal)
 111 {
 112 // reset the covariance matrix ("forget" track history)
 113
 114   Int_t k = 0;
 115   for (Int_t i = 0; i < 5; i++) {
 116     for (Int_t j = 0; j < i; j++) {  // off diagonal elements
 117       if (clearOffDiagonal) {
 118         fCovar[k++] = 0;
 119       } else {
 120         fCovar[k++] *= factor;
 121       }
 122     }
 123     fCovar[k++] *= factor;     // diagonal elements
 124   }
 125 }
 126
 127
 128 //_____________________________________________________________________________
 129 Bool_t AliExternalTrackParam::PropagateTo(Double_t /*x*/, Double_t* /*length*/)
 130 {
 131 // Propagate the track parameters to the given x coordinate assuming vacuum.
 132 // If length is not NULL, the change of track length is added to it.
 133 //
 134 // NOT IMPLEMENTED for this class
 135
 136   return kFALSE;
 137 }
 138
 139 //_____________________________________________________________________________
 140 Bool_t AliExternalTrackParam::RotateTo(Double_t /*alpha*/)
 141 {
 142 // Rotate the reference axis for the parametrisation to the given angle.
 143 //
 144 // NOT IMPLEMENTED for this class
 145
 146   return kFALSE;
 147 }
 148
 149 //_____________________________________________________________________________
 150 Bool_t AliExternalTrackParam::CorrectForMaterial(Double_t /*dAngle*/,
 151                                                  Double_t /*dPrel*/)
 152 {
 153 // Take into account material effects assuming:
 154 //   dAngle2: mean multiple scattering angle in rad squared
 155 //   dPrel  : mean relative momentum gain (if > 0) or loss (if < 0)
 156 //
 157 // NOT IMPLEMENTED for this class
 158
 159   return kFALSE;
 160 }
 161
 162 //_____________________________________________________________________________
 163 Bool_t AliExternalTrackParam::GetProlongationAt(Double_t /*x*/,
 164                                                 Double_t& /*y*/,
 165                                                 Double_t& /*z*/) const
 166 {
 167 // Get the local y and z coordinates at the given x value
 168 //
 169 // NOT IMPLEMENTED for this class
 170
 171   return kFALSE;
 172 }
 173
 174 //_____________________________________________________________________________
 175 Double_t AliExternalTrackParam::GetXAtVertex(Double_t /*x*/,
 176                                              Double_t /*y*/) const
 177 {
 178 // Get the x coordinate at the given vertex (x,y)
 179 //
 180 // NOT IMPLEMENTED for this class
 181
 182   return 0;
 183 }
 184
 185
 186 //_____________________________________________________________________________
 187 Double_t AliExternalTrackParam::GetPredictedChi2(const AliCluster* /*cluster*/)
 188 {
 189 // calculate the chi2 contribution of the given cluster
 190 //
 191 // NOT IMPLEMENTED for this class
 192
 193   return -1;
 194 }
 195
 196 //_____________________________________________________________________________
 197 Bool_t AliExternalTrackParam::Update(const AliCluster* /*cluster*/)
 198 {
 199 // update the track parameters using the position and error
 200 // of the given cluster
 201 //
 202 // NOT IMPLEMENTED for this class
 203
 204   return kFALSE;
 205 }
 206
 207
 208 //_____________________________________________________________________________
 209 Double_t AliExternalTrackParam::SigmaPhi() const
 210 {
 211 // get the error of the azimuthal angle
 212
 213   return TMath::Sqrt(TMath::Abs(fCovar[5] / (1. - fParam[2]*fParam[2])));
 214 }
 215
 216 //_____________________________________________________________________________
 217 Double_t AliExternalTrackParam::SigmaTheta() const
 218 {
 219 // get the error of the polar angle
 220
 221   return TMath::Sqrt(TMath::Abs(fCovar[9])) / (1. + fParam[3]*fParam[3]);
 222 }
 223
 224 //_____________________________________________________________________________
 225 Double_t AliExternalTrackParam::SigmaPt() const
 226 {
 227 // get the error of the transversal component of the momentum
 228
 229   return TMath::Sqrt(fCovar[14]) / TMath::Abs(fParam[4]);
 230 }
 231
 232 //_____________________________________________________________________________
 233 TVector3 AliExternalTrackParam::Momentum() const
 234 {
 235 // get the momentum vector
 236
 237   Double_t phi = TMath::ASin(fParam[2]) + fAlpha;
 238   Double_t pt = 1. / TMath::Abs(fParam[4]);
 239   return TVector3(pt * TMath::Cos(phi),
 240                   pt * TMath::Sin(phi),
 241                   pt * fParam[3]);
 242 }
 243
 244 //_____________________________________________________________________________
 245 TVector3 AliExternalTrackParam::Position() const
 246 {
 247 // get the current spatial position in global coordinates
 248
 249   return TVector3(fX * TMath::Cos(fAlpha) - fParam[0] * TMath::Sin(fAlpha),
 250                   fX * TMath::Sin(fAlpha) + fParam[0] * TMath::Cos(fAlpha),
 251                   fParam[1]);
 252 }
 253
 254
 255 //_____________________________________________________________________________
 256 void AliExternalTrackParam::Print(Option_t* /*option*/) const
 257 {
 258 // print the parameters and the covariance matrix
 259
 260   printf("AliExternalTrackParam: x = %-12g  alpha = %-12g\n", fX, fAlpha);
 261   printf("  parameters: %12g %12g %12g %12g %12g\n",
 262          fParam[0], fParam[1], fParam[2], fParam[3], fParam[4]);
 263   printf("  covariance: %12g\n", fCovar[0]);
 264   printf("              %12g %12g\n", fCovar[1], fCovar[2]);
 265   printf("              %12g %12g %12g\n", fCovar[3], fCovar[4], fCovar[5]);
 266   printf("              %12g %12g %12g %12g\n",
 267          fCovar[6], fCovar[7], fCovar[8], fCovar[9]);
 268   printf("              %12g %12g %12g %12g %12g\n",
 269          fCovar[10], fCovar[11], fCovar[12], fCovar[13], fCovar[14]);
 270 }