TRD/AliTRDseedV1.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
   5  * Contributors are mentioned in the code where appropriate.              *
   6  *                                                                        *
   7  * Permission to use, copy, modify and distribute this software and its   *
   8  * documentation strictly for non-commercial purposes is hereby granted   *
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  10  * copies and that both the copyright notice and this permission notice   *
  11  * appear in the supporting documentation. The authors make no claims     *
  12  * about the suitability of this software for any purpose. It is          *
  13  * provided "as is" without express or implied warranty.                  *
  14  **************************************************************************/
  15
  16 /* $Id$ */
  17
  18 ////////////////////////////////////////////////////////////////////////////
  19 //                                                                        //
  20 //  The TRD track seed                                                    //
  21 //                                                                        //
  22 //  Authors:                                                              //
  23 //    Alex Bercuci <A.Bercuci@gsi.de>                                     //
  24 //    Markus Fasel <M.Fasel@gsi.de>                                       //
  25 //                                                                        //
  26 ////////////////////////////////////////////////////////////////////////////
  27
  28 #include "TMath.h"
  29 #include "TLinearFitter.h"
  30 #include "TClonesArray.h" // tmp
  31 #include <TTreeStream.h>
  32
  33 #include "AliLog.h"
  34 #include "AliMathBase.h"
  35
  36 #include "AliTRDseedV1.h"
  37 #include "AliTRDcluster.h"
  38 #include "AliTRDtrack.h"
  39 #include "AliTRDcalibDB.h"
  40 #include "AliTRDchamberTimeBin.h"
  41 #include "AliTRDtrackingChamber.h"
  42 #include "AliTRDtrackerV1.h"
  43 #include "AliTRDReconstructor.h"
  44 #include "AliTRDrecoParam.h"
  45 #include "AliTRDgeometry.h"
  46 #include "Cal/AliTRDCalPID.h"
  47
  48 ClassImp(AliTRDseedV1)
  49
  50 //____________________________________________________________________
  51 AliTRDseedV1::AliTRDseedV1(Int_t plane)
  52   :AliTRDseed()
  53   ,fPlane(plane)
  54   ,fOwner(kFALSE)
  55   ,fMom(0.)
  56   ,fSnp(0.)
  57   ,fTgl(0.)
  58   ,fdX(0.)
  59 {
  60   //
  61   // Constructor
  62   //
  63         for(int islice=0; islice < knSlices; islice++) fdEdx[islice] = 0.;
  64         for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) fProb[ispec]  = -1.;
  65 }
  66
  67 //____________________________________________________________________
  68 AliTRDseedV1::AliTRDseedV1(const AliTRDseedV1 &ref)
  69   :AliTRDseed((AliTRDseed&)ref)
  70   ,fPlane(ref.fPlane)
  71   ,fOwner(kFALSE)
  72   ,fMom(ref.fMom)
  73   ,fSnp(ref.fSnp)
  74   ,fTgl(ref.fTgl)
  75   ,fdX(ref.fdX)
  76 {
  77   //
  78   // Copy Constructor performing a deep copy
  79   //
  80
  81         //AliInfo("");
  82         if(ref.fOwner) SetOwner();
  83         for(int islice=0; islice < knSlices; islice++) fdEdx[islice] = ref.fdEdx[islice];
  84         for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) fProb[ispec] = ref.fProb[ispec];
  85 }
  86
  87
  88 //____________________________________________________________________
  89 AliTRDseedV1& AliTRDseedV1::operator=(const AliTRDseedV1 &ref)
  90 {
  91   //
  92   // Assignment Operator using the copy function
  93   //
  94
  95         //AliInfo("");
  96         if(this != &ref){
  97                 ref.Copy(*this);
  98         }
  99         return *this;
 100
 101 }
 102
 103 //____________________________________________________________________
 104 AliTRDseedV1::~AliTRDseedV1()
 105 {
 106   //
 107   // Destructor. The RecoParam object belongs to the underlying tracker.
 108   //
 109
 110         //AliInfo(Form("fOwner[%s]", fOwner?"YES":"NO"));
 111
 112         if(fOwner)
 113                 for(int itb=0; itb<knTimebins; itb++){
 114                         if(!fClusters[itb]) continue;
 115                         //AliInfo(Form("deleting c %p @ %d", fClusters[itb], itb));
 116                         delete fClusters[itb];
 117                         fClusters[itb] = 0x0;
 118                 }
 119 }
 120
 121 //____________________________________________________________________
 122 void AliTRDseedV1::Copy(TObject &ref) const
 123 {
 124   //
 125   // Copy function
 126   //
 127
 128         //AliInfo("");
 129         AliTRDseedV1 &target = (AliTRDseedV1 &)ref;
 130
 131         target.fPlane         = fPlane;
 132         target.fMom           = fMom;
 133         target.fSnp           = fSnp;
 134         target.fTgl           = fTgl;
 135         target.fdX            = fdX;
 136
 137         for(int islice=0; islice < knSlices; islice++) target.fdEdx[islice] = fdEdx[islice];
 138         for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) target.fProb[ispec] = fProb[ispec];
 139
 140         AliTRDseed::Copy(target);
 141 }
 142
 143
 144 //____________________________________________________________
 145 void AliTRDseedV1::Init(AliTRDtrack *track)
 146 {
 147 // Initialize this tracklet using the track information
 148 //
 149 // Parameters:
 150 //   track - the TRD track used to initialize the tracklet
 151 //
 152 // Detailed description
 153 // The function sets the starting point and direction of the
 154 // tracklet according to the information from the TRD track.
 155 //
 156 // Caution
 157 // The TRD track has to be propagated to the beginning of the
 158 // chamber where the tracklet will be constructed
 159 //
 160
 161         Double_t y, z;
 162         track->GetProlongation(fX0, y, z);
 163         fYref[0] = y;
 164         fYref[1] = track->GetSnp()/(1. - track->GetSnp()*track->GetSnp());
 165         fZref[0] = z;
 166         fZref[1] = track->GetTgl();
 167
 168         //printf("Tracklet ref x[%7.3f] y[%7.3f] z[%7.3f], snp[%f] tgl[%f]\n", fX0, fYref[0], fZref[0], track->GetSnp(), track->GetTgl());
 169 }
 170
 171
 172 //____________________________________________________________________
 173 void AliTRDseedV1::CookdEdx(Int_t nslices)
 174 {
 175 // Calculates average dE/dx for all slices and store them in the internal array fdEdx.
 176 //
 177 // Parameters:
 178 //  nslices : number of slices for which dE/dx should be calculated
 179 // Output:
 180 //  store results in the internal array fdEdx. This can be accessed with the method
 181 //  AliTRDseedV1::GetdEdx()
 182 //
 183 // Detailed description
 184 // Calculates average dE/dx for all slices. Depending on the PID methode
 185 // the number of slices can be 3 (LQ) or 8(NN).
 186 // The calculation of dQ/dl are done using the tracklet fit results (see AliTRDseedV1::GetdQdl(Int_t)) i.e.
 187 //
 188 // dQ/dl = qc/(dx * sqrt(1 + dy/dx^2 + dz/dx^2))
 189 //
 190 // The following effects are included in the calculation:
 191 // 1. calibration values for t0 and vdrift (using x coordinate to calculate slice)
 192 // 2. cluster sharing (optional see AliTRDrecoParam::SetClusterSharing())
 193 // 3. cluster size
 194 //
 195
 196         Int_t nclusters[knSlices];
 197         for(int i=0; i<knSlices; i++){
 198                 fdEdx[i]     = 0.;
 199                 nclusters[i] = 0;
 200         }
 201         Float_t clength = (/*.5 * */AliTRDgeometry::AmThick() + AliTRDgeometry::DrThick());
 202
 203         AliTRDcluster *cluster = 0x0;
 204         for(int ic=0; ic<AliTRDtrackerV1::GetNTimeBins(); ic++){
 205                 if(!(cluster = fClusters[ic])) continue;
 206                 Float_t x = cluster->GetX();
 207
 208                 // Filter clusters for dE/dx calculation
 209
 210                 // 1.consider calibration effects for slice determination
 211                 Int_t slice;
 212                 if(cluster->IsInChamber()) slice = Int_t(TMath::Abs(fX0 - x) * nslices / clength);
 213                 else slice = x < fX0 ? 0 : nslices-1;
 214
 215                 // 2. take sharing into account
 216                 Float_t w = cluster->IsShared() ? .5 : 1.;
 217
 218                 // 3. take into account large clusters TODO
 219                 //w *= c->GetNPads() > 3 ? .8 : 1.;
 220
 221                 //CHECK !!!
 222                 fdEdx[slice]   += w * GetdQdl(ic); //fdQdl[ic];
 223                 nclusters[slice]++;
 224         } // End of loop over clusters
 225
 226         // calculate mean charge per slice
 227         for(int is=0; is<nslices; is++) if(nclusters[is]) fdEdx[is] /= nclusters[is];
 228 }
 229
 230 //____________________________________________________________________
 231 Float_t AliTRDseedV1::GetdQdl(Int_t ic) const
 232 {
 233         return fClusters[ic] ? TMath::Abs(fClusters[ic]->GetQ()) /fdX / TMath::Sqrt(1. + fYfit[1]*fYfit[1] + fZfit[1]*fZfit[1]) : 0.;
 234 }
 235
 236 //____________________________________________________________________
 237 Double_t* AliTRDseedV1::GetProbability()
 238 {
 239 // Fill probability array for tracklet from the DB.
 240 //
 241 // Parameters
 242 //
 243 // Output
 244 //   returns pointer to the probability array and 0x0 if missing DB access
 245 //
 246 // Detailed description
 247
 248
 249         // retrive calibration db
 250   AliTRDcalibDB *calibration = AliTRDcalibDB::Instance();
 251   if (!calibration) {
 252     AliError("No access to calibration data");
 253     return 0x0;
 254   }
 255
 256   // Retrieve the CDB container class with the parametric detector response
 257   const AliTRDCalPID *pd = calibration->GetPIDObject(AliTRDReconstructor::RecoParam()->GetPIDMethod());
 258   if (!pd) {
 259     AliError("No access to AliTRDCalPID object");
 260     return 0x0;
 261   }
 262
 263         // calculate tracklet length TO DO
 264   Float_t length = (AliTRDgeometry::AmThick() + AliTRDgeometry::DrThick());
 265   /// TMath::Sqrt((1.0 - fSnp[iPlane]*fSnp[iPlane]) / (1.0 + fTgl[iPlane]*fTgl[iPlane]));
 266
 267   //calculate dE/dx
 268   CookdEdx(AliTRDReconstructor::RecoParam()->GetNdEdxSlices());
 269
 270   // Sets the a priori probabilities
 271   for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) {
 272     fProb[ispec] = pd->GetProbability(ispec, fMom, &fdEdx[0], length, fPlane);
 273   }
 274
 275         return &fProb[0];
 276 }
 277
 278 //____________________________________________________________________
 279 Float_t AliTRDseedV1::GetQuality(Bool_t kZcorr) const
 280 {
 281   //
 282   // Returns a quality measurement of the current seed
 283   //
 284
 285         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 286         return
 287                   .5 * TMath::Abs(18.0 - fN2)
 288                 + 10.* TMath::Abs(fYfit[1] - fYref[1])
 289                 + 5. * TMath::Abs(fYfit[0] - fYref[0] + zcorr)
 290                 + 2. * TMath::Abs(fMeanz - fZref[0]) / fPadLength;
 291 }
 292
 293 //____________________________________________________________________
 294 void AliTRDseedV1::GetCovAt(Double_t /*x*/, Double_t *cov) const
 295 {
 296 // Computes covariance in the y-z plane at radial point x
 297
 298         Int_t ic = 0; while (!fClusters[ic]) ic++;
 299   AliTRDcalibDB *fCalib = AliTRDcalibDB::Instance();
 300         Double_t exB         = fCalib->GetOmegaTau(fCalib->GetVdriftAverage(fClusters[ic]->GetDetector()), -AliTracker::GetBz()*0.1);
 301
 302         Double_t sy2    = fSigmaY2*fSigmaY2 + .2*(fYfit[1]-exB)*(fYfit[1]-exB);
 303         Double_t sz2    = fPadLength/12.;
 304
 305
 306         //printf("Yfit[1] %f sy20 %f SigmaY2 %f\n", fYfit[1], sy20, fSigmaY2);
 307
 308         cov[0] = sy2;
 309         cov[1] = fTilt*(sy2-sz2);
 310         cov[2] = sz2;
 311 }
 312
 313
 314 //____________________________________________________________________
 315 void AliTRDseedV1::SetOwner(Bool_t own)
 316 {
 317         //AliInfo(Form("own [%s] fOwner[%s]", own?"YES":"NO", fOwner?"YES":"NO"));
 318
 319         if(own){
 320                 for(int ic=0; ic<knTimebins; ic++){
 321                         if(!fClusters[ic]) continue;
 322                         fClusters[ic] = new AliTRDcluster(*fClusters[ic]);
 323                 }
 324                 fOwner = kTRUE;
 325         } else {
 326                 if(fOwner){
 327                         for(int ic=0; ic<knTimebins; ic++){
 328                                 if(!fClusters[ic]) continue;
 329                                 delete fClusters[ic];
 330                                 //fClusters[ic] = tracker->GetClusters(index) TODO
 331                         }
 332                 }
 333                 fOwner = kFALSE;
 334         }
 335 }
 336
 337 //____________________________________________________________________
 338 Bool_t  AliTRDseedV1::AttachClustersIter(AliTRDtrackingChamber *chamber, Float_t quality, Bool_t kZcorr, AliTRDcluster *c)
 339 {
 340   //
 341   // Iterative process to register clusters to the seed.
 342   // In iteration 0 we try only one pad-row and if quality not
 343   // sufficient we try 2 pad-rows (about 5% of tracks cross 2 pad-rows)
 344   //
 345         // debug level 7
 346         //
 347
 348         if(!AliTRDReconstructor::RecoParam()){
 349                 AliError("Seed can not be used without a valid RecoParam.");
 350                 return kFALSE;
 351         }
 352
 353         AliTRDchamberTimeBin *layer = 0x0;
 354         if(AliTRDReconstructor::StreamLevel()>=7 && c){
 355                 TClonesArray clusters("AliTRDcluster", 24);
 356                 clusters.SetOwner(kTRUE);
 357                 AliTRDcluster *cc = 0x0;
 358                 Int_t det=-1, ncl, ncls = 0;
 359                 for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 360                         if(!(layer = chamber->GetTB(iTime))) continue;
 361                         if(!(ncl = Int_t(*layer))) continue;
 362                         for(int ic=0; ic<ncl; ic++){
 363                                 cc = (*layer)[ic];
 364                                 det = cc->GetDetector();
 365                                 new(clusters[ncls++]) AliTRDcluster(*cc);
 366                         }
 367                 }
 368                 AliInfo(Form("N clusters[%d] = %d", fPlane, ncls));
 369
 370                 Int_t ref = c ? 1 : 0;
 371                 TTreeSRedirector &cstreamer = *AliTRDtrackerV1::DebugStreamer();
 372                 cstreamer << "AttachClustersIter"
 373                         << "det="        << det
 374                         << "ref="        << ref
 375                         << "clusters.="  << &clusters
 376                         << "tracklet.="  << this
 377                         << "cl.="        << c
 378                         << "\n";
 379         }
 380
 381         Float_t  tquality;
 382         Double_t kroady = AliTRDReconstructor::RecoParam()->GetRoad1y();
 383         Double_t kroadz = fPadLength * .5 + 1.;
 384
 385         // initialize configuration parameters
 386         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 387         Int_t   niter = kZcorr ? 1 : 2;
 388
 389         Double_t yexp, zexp;
 390         Int_t ncl = 0;
 391         // start seed update
 392         for (Int_t iter = 0; iter < niter; iter++) {
 393                 ncl = 0;
 394                 for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 395                         if(!(layer = chamber->GetTB(iTime))) continue;
 396                         if(!Int_t(*layer)) continue;
 397
 398                         // define searching configuration
 399                         Double_t dxlayer = layer->GetX() - fX0;
 400                         if(c){
 401                                 zexp = c->GetZ();
 402                                 //Try 2 pad-rows in second iteration
 403                                 if (iter > 0) {
 404                                         zexp = fZref[0] + fZref[1] * dxlayer - zcorr;
 405                                         if (zexp > c->GetZ()) zexp = c->GetZ() + fPadLength*0.5;
 406                                         if (zexp < c->GetZ()) zexp = c->GetZ() - fPadLength*0.5;
 407                                 }
 408                         } else zexp = fZref[0] + (kZcorr ? fZref[1] * dxlayer : 0.);
 409                         yexp  = fYref[0] + fYref[1] * dxlayer - zcorr;
 410
 411                         // Get and register cluster
 412                         Int_t    index = layer->SearchNearestCluster(yexp, zexp, kroady, kroadz);
 413                         if (index < 0) continue;
 414                         AliTRDcluster *cl = (*layer)[index];
 415
 416                         fIndexes[iTime]  = layer->GetGlobalIndex(index);
 417                         fClusters[iTime] = cl;
 418                         fY[iTime]        = cl->GetY();
 419                         fZ[iTime]        = cl->GetZ();
 420                         ncl++;
 421                 }
 422         if(AliTRDReconstructor::StreamLevel()>=7) AliInfo(Form("iter = %d ncl [%d] = %d", iter, fPlane, ncl));
 423
 424                 if(ncl>1){
 425                         // calculate length of the time bin (calibration aware)
 426                         Int_t irp = 0; Float_t x[2]; Int_t tb[2];
 427                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 428                                 if(!fClusters[iTime]) continue;
 429                                 x[irp]  = fClusters[iTime]->GetX();
 430                                 tb[irp] = iTime;
 431                                 irp++;
 432                                 if(irp==2) break;
 433                         }
 434                         fdX = (x[1] - x[0]) / (tb[0] - tb[1]);
 435
 436                         // update X0 from the clusters (calibration/alignment aware)
 437                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 438                                 if(!(layer = chamber->GetTB(iTime))) continue;
 439                                 if(!layer->IsT0()) continue;
 440                                 if(fClusters[iTime]){
 441                                         fX0 = fClusters[iTime]->GetX();
 442                                         break;
 443                                 } else { // we have to infere the position of the anode wire from the other clusters
 444                                         for (Int_t jTime = iTime+1; jTime < AliTRDtrackerV1::GetNTimeBins(); jTime++) {
 445                                                 if(!fClusters[jTime]) continue;
 446                                                 fX0 = fClusters[jTime]->GetX() + fdX * (jTime - iTime);
 447                                         }
 448                                         break;
 449                                 }
 450                         }
 451
 452                         // update YZ reference point
 453                         // TODO
 454
 455                         // update x reference positions (calibration/alignment aware)
 456                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 457                                 if(!fClusters[iTime]) continue;
 458                                 fX[iTime] = fClusters[iTime]->GetX() - fX0;
 459                         }
 460
 461                         AliTRDseed::Update();
 462                 }
 463         if(AliTRDReconstructor::StreamLevel()>=7) AliInfo(Form("iter = %d nclFit [%d] = %d", iter, fPlane, fN2));
 464
 465                 if(IsOK()){
 466                         tquality = GetQuality(kZcorr);
 467                         if(tquality < quality) break;
 468                         else quality = tquality;
 469                 }
 470                 kroadz *= 2.;
 471         } // Loop: iter
 472         if (!IsOK()) return kFALSE;
 473
 474         CookLabels();
 475         UpdateUsed();
 476         return kTRUE;
 477 }
 478
 479 //____________________________________________________________________
 480 Bool_t  AliTRDseedV1::AttachClusters(AliTRDtrackingChamber *chamber
 481                                        ,Bool_t kZcorr)
 482 {
 483   //
 484   // Projective algorithm to attach clusters to seeding tracklets
 485   //
 486   // Parameters
 487   //
 488   // Output
 489   //
 490   // Detailed description
 491   // 1. Collapse x coordinate for the full detector plane
 492   // 2. truncated mean on y (r-phi) direction
 493   // 3. purge clusters
 494   // 4. truncated mean on z direction
 495   // 5. purge clusters
 496   // 6. fit tracklet
 497   //
 498
 499         if(!AliTRDReconstructor::RecoParam()){
 500                 AliError("Seed can not be used without a valid RecoParam.");
 501                 return kFALSE;
 502         }
 503
 504         const Int_t kClusterCandidates = 2 * knTimebins;
 505
 506         //define roads
 507         Double_t kroady = AliTRDReconstructor::RecoParam()->GetRoad1y();
 508         Double_t kroadz = fPadLength * 1.5 + 1.;
 509         // correction to y for the tilting angle
 510         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 511
 512         // working variables
 513         AliTRDcluster *clusters[kClusterCandidates];
 514         Double_t cond[4], yexp[knTimebins], zexp[knTimebins],
 515                 yres[kClusterCandidates], zres[kClusterCandidates];
 516         Int_t ncl, *index = 0x0, tboundary[knTimebins];
 517
 518         // Do cluster projection
 519         AliTRDchamberTimeBin *layer = 0x0;
 520         Int_t nYclusters = 0; Bool_t kEXIT = kFALSE;
 521         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 522                 if(!(layer = chamber->GetTB(iTime))) continue;
 523                 if(!Int_t(*layer)) continue;
 524
 525                 fX[iTime] = layer->GetX() - fX0;
 526                 zexp[iTime] = fZref[0] + fZref[1] * fX[iTime];
 527                 yexp[iTime] = fYref[0] + fYref[1] * fX[iTime] - zcorr;
 528
 529                 // build condition and process clusters
 530                 cond[0] = yexp[iTime] - kroady; cond[1] = yexp[iTime] + kroady;
 531                 cond[2] = zexp[iTime] - kroadz; cond[3] = zexp[iTime] + kroadz;
 532                 layer->GetClusters(cond, index, ncl);
 533                 for(Int_t ic = 0; ic<ncl; ic++){
 534                         AliTRDcluster *c = layer->GetCluster(index[ic]);
 535                         clusters[nYclusters] = c;
 536                         yres[nYclusters++] = c->GetY() - yexp[iTime];
 537                         if(nYclusters >= kClusterCandidates) {
 538                                 AliWarning(Form("Cluster candidates reached limit %d. Some may be lost.", kClusterCandidates));
 539                                 kEXIT = kTRUE;
 540                                 break;
 541                         }
 542                 }
 543                 tboundary[iTime] = nYclusters;
 544                 if(kEXIT) break;
 545         }
 546
 547         // Evaluate truncated mean on the y direction
 548         Double_t mean, sigma;
 549         AliMathBase::EvaluateUni(nYclusters, yres, mean, sigma, Int_t(nYclusters*.8)-2);
 550         // purge cluster candidates
 551         Int_t nZclusters = 0;
 552         for(Int_t ic = 0; ic<nYclusters; ic++){
 553                 if(yres[ic] - mean > 4. * sigma){
 554                         clusters[ic] = 0x0;
 555                         continue;
 556                 }
 557                 zres[nZclusters++] = clusters[ic]->GetZ() - zexp[clusters[ic]->GetLocalTimeBin()];
 558         }
 559
 560         // Evaluate truncated mean on the z direction
 561         AliMathBase::EvaluateUni(nZclusters, zres, mean, sigma, Int_t(nZclusters*.8)-2);
 562         // purge cluster candidates
 563         for(Int_t ic = 0; ic<nZclusters; ic++){
 564                 if(zres[ic] - mean > 4. * sigma){
 565                         clusters[ic] = 0x0;
 566                         continue;
 567                 }
 568         }
 569
 570
 571         // Select only one cluster/TimeBin
 572         Int_t lastCluster = 0;
 573         fN2 = 0;
 574         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 575                 ncl = tboundary[iTime] - lastCluster;
 576                 if(!ncl) continue;
 577                 Int_t iptr = lastCluster;
 578                 if(ncl > 1){
 579                         Float_t dold = 9999.;
 580                         for(int ic=lastCluster; ic<tboundary[iTime]; ic++){
 581                                 if(!clusters[ic]) continue;
 582                                 Float_t y = yexp[iTime] - clusters[ic]->GetY();
 583                                 Float_t z = zexp[iTime] - clusters[ic]->GetZ();
 584                                 Float_t d = y * y + z * z;
 585                                 if(d > dold) continue;
 586                                 dold = d;
 587                                 iptr = ic;
 588                         }
 589                 }
 590                 fIndexes[iTime]  = chamber->GetTB(iTime)->GetGlobalIndex(iptr);
 591                 fClusters[iTime] = clusters[iptr];
 592                 fY[iTime]        = clusters[iptr]->GetY();
 593                 fZ[iTime]        = clusters[iptr]->GetZ();
 594                 lastCluster      = tboundary[iTime];
 595                 fN2++;
 596         }
 597
 598         // number of minimum numbers of clusters expected for the tracklet
 599         Int_t kClmin = Int_t(AliTRDReconstructor::RecoParam()->GetFindableClusters()*AliTRDtrackerV1::GetNTimeBins());
 600   if (fN2 < kClmin){
 601                 AliWarning(Form("Not enough clusters to fit the tracklet %d [%d].", fN2, kClmin));
 602     fN2 = 0;
 603     return kFALSE;
 604   }
 605
 606         // update used clusters
 607         fNUsed = 0;
 608         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 609                 if(!fClusters[iTime]) continue;
 610                 if((fClusters[iTime]->IsUsed())) fNUsed++;
 611         }
 612
 613   if (fN2-fNUsed < kClmin){
 614                 AliWarning(Form("Too many clusters already in use %d (from %d).", fNUsed, fN2));
 615     fN2 = 0;
 616     return kFALSE;
 617   }
 618
 619         return kTRUE;
 620 }
 621
 622 //____________________________________________________________________
 623 Bool_t AliTRDseedV1::Fit()
 624 {
 625   //
 626   // Linear fit of the tracklet
 627   //
 628   // Parameters :
 629   //
 630   // Output :
 631   //  True if successful
 632   //
 633   // Detailed description
 634   // 2. Check if tracklet crosses pad row boundary
 635   // 1. Calculate residuals in the y (r-phi) direction
 636   // 3. Do a Least Square Fit to the data
 637   //
 638
 639         //Float_t  sigmaexp  = 0.05 + TMath::Abs(fYref[1] * 0.25); // Expected r.m.s in y direction
 640   Float_t  ycrosscor = fPadLength * fTilt * 0.5; // Y correction for crossing
 641   Float_t  anglecor = fTilt * fZref[1];  // Correction to the angle
 642
 643         // calculate residuals
 644         Float_t yres[knTimebins]; // y (r-phi) residuals
 645         Int_t zint[knTimebins],   // Histograming of the z coordinate
 646               zout[2*knTimebins];//
 647
 648         fN = 0;
 649         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 650     if (!fClusters[iTime]) continue;
 651     if (!fClusters[iTime]->IsInChamber()) continue;
 652     yres[iTime] = fY[iTime] - fYref[0] - (fYref[1] + anglecor) * fX[iTime] + fTilt * (fZ[iTime] - fZref[0]);
 653                 zint[fN] = Int_t(fZ[iTime]);
 654                 fN++;
 655         }
 656
 657         // calculate pad row boundary crosses
 658         Int_t kClmin = Int_t(AliTRDReconstructor::RecoParam()->GetFindableClusters()*AliTRDtrackerV1::GetNTimeBins());
 659         Int_t nz = AliMathBase::Freq(fN, zint, zout, kFALSE);
 660   fZProb   = zout[0];
 661   if(nz <= 1) zout[3] = 0;
 662   if(zout[1] + zout[3] < kClmin) {
 663                 AliWarning(Form("Not enough clusters to fit the cross boundary tracklet %d [%d].", zout[1]+zout[3], kClmin));
 664                 return kFALSE;
 665         }
 666   // Z distance bigger than pad - length
 667   if (TMath::Abs(zout[0]-zout[2]) > fPadLength) zout[3]=0;
 668
 669
 670   Double_t sumw   = 0.,
 671                 sumwx  = 0.,
 672                 sumwx2 = 0.,
 673                 sumwy  = 0.,
 674                 sumwxy = 0.,
 675                 sumwz  = 0.,
 676                 sumwxz = 0.;
 677         Int_t npads;
 678   fMPads = 0;
 679         fMeanz = 0.;
 680         // we will use only the clusters which are in the detector range
 681         for(int iTime=0; iTime<AliTRDtrackerV1::GetNTimeBins(); iTime++){
 682     fUsable[iTime] = kFALSE;
 683     if (!fClusters[iTime]) continue;
 684                 npads = fClusters[iTime]->GetNPads();
 685
 686                 fUsable[iTime] = kTRUE;
 687     fN2++;
 688     fMPads += npads;
 689     Float_t weight = 1.0;
 690     if(npads > 5) weight = 0.2;
 691     else if(npads > 4) weight = 0.5;
 692     sumw   += weight;
 693     sumwx  += fX[iTime] * weight;
 694     sumwx2 += fX[iTime] * fX[iTime] * weight;
 695     sumwy  += weight * yres[iTime];
 696     sumwxy += weight * yres[iTime] * fX[iTime];
 697     sumwz  += weight * fZ[iTime];
 698     sumwxz += weight * fZ[iTime] * fX[iTime];
 699         }
 700   if (fN2 < kClmin){
 701                 AliWarning(Form("Not enough clusters to fit the tracklet %d [%d].", fN2, kClmin));
 702     fN2 = 0;
 703     return kFALSE;
 704   }
 705   fMeanz = sumwz / sumw;
 706         fNChange = 0;
 707
 708         // Tracklet on boundary
 709   Float_t correction = 0;
 710   if (fNChange > 0) {
 711     if (fMeanz < fZProb) correction =  ycrosscor;
 712     if (fMeanz > fZProb) correction = -ycrosscor;
 713   }
 714
 715   Double_t det = sumw * sumwx2 - sumwx * sumwx;
 716   fYfitR[0]    = (sumwx2 * sumwy  - sumwx * sumwxy) / det;
 717   fYfitR[1]    = (sumw   * sumwxy - sumwx * sumwy)  / det;
 718
 719   fSigmaY2 = 0;
 720   for (Int_t i = 0; i < AliTRDtrackerV1::GetNTimeBins()+1; i++) {
 721     if (!fUsable[i]) continue;
 722     Float_t delta = yres[i] - fYfitR[0] - fYfitR[1] * fX[i];
 723     fSigmaY2 += delta*delta;
 724   }
 725   fSigmaY2 = TMath::Sqrt(fSigmaY2 / Float_t(fN2-2));
 726
 727   fZfitR[0]  = (sumwx2 * sumwz  - sumwx * sumwxz) / det;
 728   fZfitR[1]  = (sumw   * sumwxz - sumwx * sumwz)  / det;
 729   fZfit[0]   = (sumwx2 * sumwz  - sumwx * sumwxz) / det;
 730   fZfit[1]   = (sumw   * sumwxz - sumwx * sumwz)  / det;
 731   fYfitR[0] += fYref[0] + correction;
 732   fYfitR[1] += fYref[1];
 733   fYfit[0]   = fYfitR[0];
 734   fYfit[1]   = fYfitR[1];
 735
 736         return kTRUE;
 737 }
 738
 739
 740 //___________________________________________________________________
 741 void AliTRDseedV1::Print()
 742 {
 743   //
 744   // Printing the seedstatus
 745   //
 746
 747         printf("Seed status :\n");
 748         printf("  fTilt      = %f\n", fTilt);
 749         printf("  fPadLength = %f\n", fPadLength);
 750         printf("  fX0        = %f\n", fX0);
 751         for(int ic=0; ic<AliTRDtrackerV1::GetNTimeBins(); ic++) {
 752           const Char_t *isUsable = fUsable[ic]?"Yes":"No";
 753           printf("  %d X[%f] Y[%f] Z[%f] Indexes[%d] clusters[%p] usable[%s]\n"
 754                 , ic
 755                 , fX[ic]
 756                 , fY[ic]
 757                 , fZ[ic]
 758                 , fIndexes[ic]
 759                 , ((void*) fClusters[ic])
 760                 , isUsable);
 761         }
 762
 763         printf("  fYref[0] =%f fYref[1] =%f\n", fYref[0], fYref[1]);
 764         printf("  fZref[0] =%f fZref[1] =%f\n", fZref[0], fZref[1]);
 765         printf("  fYfit[0] =%f fYfit[1] =%f\n", fYfit[0], fYfit[1]);
 766         printf("  fYfitR[0]=%f fYfitR[1]=%f\n", fYfitR[0], fYfitR[1]);
 767         printf("  fZfit[0] =%f fZfit[1] =%f\n", fZfit[0], fZfit[1]);
 768         printf("  fZfitR[0]=%f fZfitR[1]=%f\n", fZfitR[0], fZfitR[1]);
 769         printf("  fSigmaY =%f\n", fSigmaY);
 770         printf("  fSigmaY2=%f\n", fSigmaY2);
 771         printf("  fMeanz  =%f\n", fMeanz);
 772         printf("  fZProb  =%f\n", fZProb);
 773         printf("  fLabels[0]=%d fLabels[1]=%d\n", fLabels[0], fLabels[1]);
 774         printf("  fN      =%d\n", fN);
 775         printf("  fN2     =%d (>8 isOK)\n",fN2);
 776         printf("  fNUsed  =%d\n", fNUsed);
 777         printf("  fFreq   =%d\n", fFreq);
 778         printf("  fNChange=%d\n",  fNChange);
 779         printf("  fMPads  =%f\n", fMPads);
 780
 781         printf("  fC      =%f\n", fC);
 782         printf("  fCC     =%f\n",fCC);
 783         printf("  fChi2   =%f\n", fChi2);
 784         printf("  fChi2Z  =%f\n", fChi2Z);
 785
 786 }