TRD/AliTRDseedV1.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
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   6  *                                                                        *
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  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   ,fMom(0.)
  55   ,fSnp(0.)
  56   ,fTgl(0.)
  57   ,fdX(0.)
  58 {
  59   //
  60   // Constructor
  61   //
  62         for(int islice=0; islice < knSlices; islice++) fdEdx[islice] = 0.;
  63         for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) fProb[ispec]  = -1.;
  64 }
  65
  66 //____________________________________________________________________
  67 AliTRDseedV1::AliTRDseedV1(const AliTRDseedV1 &ref)
  68   :AliTRDseed((AliTRDseed&)ref)
  69   ,fPlane(ref.fPlane)
  70   ,fMom(ref.fMom)
  71   ,fSnp(ref.fSnp)
  72   ,fTgl(ref.fTgl)
  73   ,fdX(ref.fdX)
  74 {
  75   //
  76   // Copy Constructor performing a deep copy
  77   //
  78
  79         //AliInfo("");
  80         for(int islice=0; islice < knSlices; islice++) fdEdx[islice] = ref.fdEdx[islice];
  81         for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) fProb[ispec] = ref.fProb[ispec];
  82 }
  83
  84
  85 //____________________________________________________________________
  86 AliTRDseedV1& AliTRDseedV1::operator=(const AliTRDseedV1 &ref)
  87 {
  88   //
  89   // Assignment Operator using the copy function
  90   //
  91
  92         //AliInfo("");
  93         if(this != &ref){
  94                 ref.Copy(*this);
  95         }
  96         return *this;
  97
  98 }
  99
 100 //____________________________________________________________________
 101 AliTRDseedV1::~AliTRDseedV1()
 102 {
 103   //
 104   // Destructor. The RecoParam object belongs to the underlying tracker.
 105   //
 106
 107         //AliInfo(Form("fOwner[%s]", fOwner?"YES":"NO"));
 108
 109         if(IsOwner())
 110                 for(int itb=0; itb<knTimebins; itb++){
 111                         if(!fClusters[itb]) continue;
 112                         //AliInfo(Form("deleting c %p @ %d", fClusters[itb], itb));
 113                         delete fClusters[itb];
 114                         fClusters[itb] = 0x0;
 115                 }
 116 }
 117
 118 //____________________________________________________________________
 119 void AliTRDseedV1::Copy(TObject &ref) const
 120 {
 121   //
 122   // Copy function
 123   //
 124
 125         //AliInfo("");
 126         AliTRDseedV1 &target = (AliTRDseedV1 &)ref;
 127
 128         target.fPlane         = fPlane;
 129         target.fMom           = fMom;
 130         target.fSnp           = fSnp;
 131         target.fTgl           = fTgl;
 132         target.fdX            = fdX;
 133
 134         for(int islice=0; islice < knSlices; islice++) target.fdEdx[islice] = fdEdx[islice];
 135         for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) target.fProb[ispec] = fProb[ispec];
 136
 137         AliTRDseed::Copy(target);
 138 }
 139
 140
 141 //____________________________________________________________
 142 void AliTRDseedV1::Init(AliTRDtrack *track)
 143 {
 144 // Initialize this tracklet using the track information
 145 //
 146 // Parameters:
 147 //   track - the TRD track used to initialize the tracklet
 148 //
 149 // Detailed description
 150 // The function sets the starting point and direction of the
 151 // tracklet according to the information from the TRD track.
 152 //
 153 // Caution
 154 // The TRD track has to be propagated to the beginning of the
 155 // chamber where the tracklet will be constructed
 156 //
 157
 158         Double_t y, z;
 159         track->GetProlongation(fX0, y, z);
 160         fYref[0] = y;
 161         fYref[1] = track->GetSnp()/(1. - track->GetSnp()*track->GetSnp());
 162         fZref[0] = z;
 163         fZref[1] = track->GetTgl();
 164
 165         //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());
 166 }
 167
 168
 169 //____________________________________________________________________
 170 void AliTRDseedV1::CookdEdx(Int_t nslices)
 171 {
 172 // Calculates average dE/dx for all slices and store them in the internal array fdEdx.
 173 //
 174 // Parameters:
 175 //  nslices : number of slices for which dE/dx should be calculated
 176 // Output:
 177 //  store results in the internal array fdEdx. This can be accessed with the method
 178 //  AliTRDseedV1::GetdEdx()
 179 //
 180 // Detailed description
 181 // Calculates average dE/dx for all slices. Depending on the PID methode
 182 // the number of slices can be 3 (LQ) or 8(NN).
 183 // The calculation of dQ/dl are done using the tracklet fit results (see AliTRDseedV1::GetdQdl(Int_t)) i.e.
 184 //
 185 // dQ/dl = qc/(dx * sqrt(1 + dy/dx^2 + dz/dx^2))
 186 //
 187 // The following effects are included in the calculation:
 188 // 1. calibration values for t0 and vdrift (using x coordinate to calculate slice)
 189 // 2. cluster sharing (optional see AliTRDrecoParam::SetClusterSharing())
 190 // 3. cluster size
 191 //
 192
 193         Int_t nclusters[knSlices];
 194         for(int i=0; i<knSlices; i++){
 195                 fdEdx[i]     = 0.;
 196                 nclusters[i] = 0;
 197         }
 198         Float_t clength = (/*.5 * */AliTRDgeometry::AmThick() + AliTRDgeometry::DrThick());
 199
 200         AliTRDcluster *cluster = 0x0;
 201         for(int ic=0; ic<AliTRDtrackerV1::GetNTimeBins(); ic++){
 202                 if(!(cluster = fClusters[ic])) continue;
 203                 Float_t x = cluster->GetX();
 204
 205                 // Filter clusters for dE/dx calculation
 206
 207                 // 1.consider calibration effects for slice determination
 208                 Int_t slice;
 209                 if(cluster->IsInChamber()) slice = Int_t(TMath::Abs(fX0 - x) * nslices / clength);
 210                 else slice = x < fX0 ? 0 : nslices-1;
 211
 212                 // 2. take sharing into account
 213                 Float_t w = cluster->IsShared() ? .5 : 1.;
 214
 215                 // 3. take into account large clusters TODO
 216                 //w *= c->GetNPads() > 3 ? .8 : 1.;
 217
 218                 //CHECK !!!
 219                 fdEdx[slice]   += w * GetdQdl(ic); //fdQdl[ic];
 220                 nclusters[slice]++;
 221         } // End of loop over clusters
 222
 223         // calculate mean charge per slice
 224         for(int is=0; is<nslices; is++) if(nclusters[is]) fdEdx[is] /= nclusters[is];
 225 }
 226
 227 //____________________________________________________________________
 228 Float_t AliTRDseedV1::GetdQdl(Int_t ic) const
 229 {
 230         return fClusters[ic] ? TMath::Abs(fClusters[ic]->GetQ()) /fdX / TMath::Sqrt(1. + fYfit[1]*fYfit[1] + fZfit[1]*fZfit[1]) : 0.;
 231 }
 232
 233 //____________________________________________________________________
 234 Double_t* AliTRDseedV1::GetProbability()
 235 {
 236 // Fill probability array for tracklet from the DB.
 237 //
 238 // Parameters
 239 //
 240 // Output
 241 //   returns pointer to the probability array and 0x0 if missing DB access
 242 //
 243 // Detailed description
 244
 245
 246         // retrive calibration db
 247   AliTRDcalibDB *calibration = AliTRDcalibDB::Instance();
 248   if (!calibration) {
 249     AliError("No access to calibration data");
 250     return 0x0;
 251   }
 252
 253   // Retrieve the CDB container class with the parametric detector response
 254   const AliTRDCalPID *pd = calibration->GetPIDObject(AliTRDReconstructor::RecoParam()->GetPIDMethod());
 255   if (!pd) {
 256     AliError("No access to AliTRDCalPID object");
 257     return 0x0;
 258   }
 259
 260         // calculate tracklet length TO DO
 261   Float_t length = (AliTRDgeometry::AmThick() + AliTRDgeometry::DrThick());
 262   /// TMath::Sqrt((1.0 - fSnp[iPlane]*fSnp[iPlane]) / (1.0 + fTgl[iPlane]*fTgl[iPlane]));
 263
 264   //calculate dE/dx
 265   CookdEdx(AliTRDReconstructor::RecoParam()->GetNdEdxSlices());
 266
 267   // Sets the a priori probabilities
 268   for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) {
 269     fProb[ispec] = pd->GetProbability(ispec, fMom, &fdEdx[0], length, fPlane);
 270   }
 271
 272         return &fProb[0];
 273 }
 274
 275 //____________________________________________________________________
 276 Float_t AliTRDseedV1::GetQuality(Bool_t kZcorr) const
 277 {
 278   //
 279   // Returns a quality measurement of the current seed
 280   //
 281
 282         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 283         return
 284                   .5 * TMath::Abs(18.0 - fN2)
 285                 + 10.* TMath::Abs(fYfit[1] - fYref[1])
 286                 + 5. * TMath::Abs(fYfit[0] - fYref[0] + zcorr)
 287                 + 2. * TMath::Abs(fMeanz - fZref[0]) / fPadLength;
 288 }
 289
 290 //____________________________________________________________________
 291 void AliTRDseedV1::GetCovAt(Double_t /*x*/, Double_t *cov) const
 292 {
 293 // Computes covariance in the y-z plane at radial point x
 294
 295         Int_t ic = 0; while (!fClusters[ic]) ic++;
 296   AliTRDcalibDB *fCalib = AliTRDcalibDB::Instance();
 297         Double_t exB         = fCalib->GetOmegaTau(fCalib->GetVdriftAverage(fClusters[ic]->GetDetector()), -AliTracker::GetBz()*0.1);
 298
 299         Double_t sy2    = fSigmaY2*fSigmaY2 + .2*(fYfit[1]-exB)*(fYfit[1]-exB);
 300         Double_t sz2    = fPadLength/12.;
 301
 302
 303         //printf("Yfit[1] %f sy20 %f SigmaY2 %f\n", fYfit[1], sy20, fSigmaY2);
 304
 305         cov[0] = sy2;
 306         cov[1] = fTilt*(sy2-sz2);
 307         cov[2] = sz2;
 308 }
 309
 310
 311 //____________________________________________________________________
 312 void AliTRDseedV1::SetOwner(Bool_t own)
 313 {
 314         //AliInfo(Form("own [%s] fOwner[%s]", own?"YES":"NO", fOwner?"YES":"NO"));
 315
 316         if(own){
 317                 for(int ic=0; ic<knTimebins; ic++){
 318                         if(!fClusters[ic]) continue;
 319                         fClusters[ic] = new AliTRDcluster(*fClusters[ic]);
 320                 }
 321                 SetBit(1);
 322         } else {
 323                 if(IsOwner()){
 324                         for(int ic=0; ic<knTimebins; ic++){
 325                                 if(!fClusters[ic]) continue;
 326                                 delete fClusters[ic];
 327                                 //fClusters[ic] = tracker->GetClusters(index) TODO
 328                         }
 329                 }
 330                 SetBit(1, kFALSE);
 331         }
 332 }
 333
 334 //____________________________________________________________________
 335 Bool_t  AliTRDseedV1::AttachClustersIter(AliTRDtrackingChamber *chamber, Float_t quality, Bool_t kZcorr, AliTRDcluster *c)
 336 {
 337   //
 338   // Iterative process to register clusters to the seed.
 339   // In iteration 0 we try only one pad-row and if quality not
 340   // sufficient we try 2 pad-rows (about 5% of tracks cross 2 pad-rows)
 341   //
 342         // debug level 7
 343         //
 344
 345         if(!AliTRDReconstructor::RecoParam()){
 346                 AliError("Seed can not be used without a valid RecoParam.");
 347                 return kFALSE;
 348         }
 349
 350         AliTRDchamberTimeBin *layer = 0x0;
 351         if(AliTRDReconstructor::StreamLevel()>=7 && c){
 352                 TClonesArray clusters("AliTRDcluster", 24);
 353                 clusters.SetOwner(kTRUE);
 354                 AliTRDcluster *cc = 0x0;
 355                 Int_t det=-1, ncl, ncls = 0;
 356                 for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 357                         if(!(layer = chamber->GetTB(iTime))) continue;
 358                         if(!(ncl = Int_t(*layer))) continue;
 359                         for(int ic=0; ic<ncl; ic++){
 360                                 cc = (*layer)[ic];
 361                                 det = cc->GetDetector();
 362                                 new(clusters[ncls++]) AliTRDcluster(*cc);
 363                         }
 364                 }
 365                 AliInfo(Form("N clusters[%d] = %d", fPlane, ncls));
 366
 367                 Int_t ref = c ? 1 : 0;
 368                 TTreeSRedirector &cstreamer = *AliTRDtrackerV1::DebugStreamer();
 369                 cstreamer << "AttachClustersIter"
 370                         << "det="        << det
 371                         << "ref="        << ref
 372                         << "clusters.="  << &clusters
 373                         << "tracklet.="  << this
 374                         << "cl.="        << c
 375                         << "\n";
 376         }
 377
 378         Float_t  tquality;
 379         Double_t kroady = AliTRDReconstructor::RecoParam()->GetRoad1y();
 380         Double_t kroadz = fPadLength * .5 + 1.;
 381
 382         // initialize configuration parameters
 383         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 384         Int_t   niter = kZcorr ? 1 : 2;
 385
 386         Double_t yexp, zexp;
 387         Int_t ncl = 0;
 388         // start seed update
 389         for (Int_t iter = 0; iter < niter; iter++) {
 390                 ncl = 0;
 391                 for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 392                         if(!(layer = chamber->GetTB(iTime))) continue;
 393                         if(!Int_t(*layer)) continue;
 394
 395                         // define searching configuration
 396                         Double_t dxlayer = layer->GetX() - fX0;
 397                         if(c){
 398                                 zexp = c->GetZ();
 399                                 //Try 2 pad-rows in second iteration
 400                                 if (iter > 0) {
 401                                         zexp = fZref[0] + fZref[1] * dxlayer - zcorr;
 402                                         if (zexp > c->GetZ()) zexp = c->GetZ() + fPadLength*0.5;
 403                                         if (zexp < c->GetZ()) zexp = c->GetZ() - fPadLength*0.5;
 404                                 }
 405                         } else zexp = fZref[0] + (kZcorr ? fZref[1] * dxlayer : 0.);
 406                         yexp  = fYref[0] + fYref[1] * dxlayer - zcorr;
 407
 408                         // Get and register cluster
 409                         Int_t    index = layer->SearchNearestCluster(yexp, zexp, kroady, kroadz);
 410                         if (index < 0) continue;
 411                         AliTRDcluster *cl = (*layer)[index];
 412
 413                         fIndexes[iTime]  = layer->GetGlobalIndex(index);
 414                         fClusters[iTime] = cl;
 415                         fY[iTime]        = cl->GetY();
 416                         fZ[iTime]        = cl->GetZ();
 417                         ncl++;
 418                 }
 419         if(AliTRDReconstructor::StreamLevel()>=7) AliInfo(Form("iter = %d ncl [%d] = %d", iter, fPlane, ncl));
 420
 421                 if(ncl>1){
 422                         // calculate length of the time bin (calibration aware)
 423                         Int_t irp = 0; Float_t x[2]; Int_t tb[2];
 424                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 425                                 if(!fClusters[iTime]) continue;
 426                                 x[irp]  = fClusters[iTime]->GetX();
 427                                 tb[irp] = iTime;
 428                                 irp++;
 429                                 if(irp==2) break;
 430                         }
 431                         fdX = (x[1] - x[0]) / (tb[0] - tb[1]);
 432
 433                         // update X0 from the clusters (calibration/alignment aware)
 434                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 435                                 if(!(layer = chamber->GetTB(iTime))) continue;
 436                                 if(!layer->IsT0()) continue;
 437                                 if(fClusters[iTime]){
 438                                         fX0 = fClusters[iTime]->GetX();
 439                                         break;
 440                                 } else { // we have to infere the position of the anode wire from the other clusters
 441                                         for (Int_t jTime = iTime+1; jTime < AliTRDtrackerV1::GetNTimeBins(); jTime++) {
 442                                                 if(!fClusters[jTime]) continue;
 443                                                 fX0 = fClusters[jTime]->GetX() + fdX * (jTime - iTime);
 444                                         }
 445                                         break;
 446                                 }
 447                         }
 448
 449                         // update YZ reference point
 450                         // TODO
 451
 452                         // update x reference positions (calibration/alignment aware)
 453                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 454                                 if(!fClusters[iTime]) continue;
 455                                 fX[iTime] = fClusters[iTime]->GetX() - fX0;
 456                         }
 457
 458                         AliTRDseed::Update();
 459                 }
 460         if(AliTRDReconstructor::StreamLevel()>=7) AliInfo(Form("iter = %d nclFit [%d] = %d", iter, fPlane, fN2));
 461
 462                 if(IsOK()){
 463                         tquality = GetQuality(kZcorr);
 464                         if(tquality < quality) break;
 465                         else quality = tquality;
 466                 }
 467                 kroadz *= 2.;
 468         } // Loop: iter
 469         if (!IsOK()) return kFALSE;
 470
 471         CookLabels();
 472         UpdateUsed();
 473         return kTRUE;
 474 }
 475
 476 //____________________________________________________________________
 477 Bool_t  AliTRDseedV1::AttachClusters(AliTRDtrackingChamber *chamber
 478                                        ,Bool_t kZcorr)
 479 {
 480   //
 481   // Projective algorithm to attach clusters to seeding tracklets
 482   //
 483   // Parameters
 484   //
 485   // Output
 486   //
 487   // Detailed description
 488   // 1. Collapse x coordinate for the full detector plane
 489   // 2. truncated mean on y (r-phi) direction
 490   // 3. purge clusters
 491   // 4. truncated mean on z direction
 492   // 5. purge clusters
 493   // 6. fit tracklet
 494   //
 495
 496         if(!AliTRDReconstructor::RecoParam()){
 497                 AliError("Seed can not be used without a valid RecoParam.");
 498                 return kFALSE;
 499         }
 500
 501         const Int_t kClusterCandidates = 2 * knTimebins;
 502
 503         //define roads
 504         Double_t kroady = AliTRDReconstructor::RecoParam()->GetRoad1y();
 505         Double_t kroadz = fPadLength * 1.5 + 1.;
 506         // correction to y for the tilting angle
 507         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 508
 509         // working variables
 510         AliTRDcluster *clusters[kClusterCandidates];
 511         Double_t cond[4], yexp[knTimebins], zexp[knTimebins],
 512                 yres[kClusterCandidates], zres[kClusterCandidates];
 513         Int_t ncl, *index = 0x0, tboundary[knTimebins];
 514
 515         // Do cluster projection
 516         AliTRDchamberTimeBin *layer = 0x0;
 517         Int_t nYclusters = 0; Bool_t kEXIT = kFALSE;
 518         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 519                 if(!(layer = chamber->GetTB(iTime))) continue;
 520                 if(!Int_t(*layer)) continue;
 521
 522                 fX[iTime] = layer->GetX() - fX0;
 523                 zexp[iTime] = fZref[0] + fZref[1] * fX[iTime];
 524                 yexp[iTime] = fYref[0] + fYref[1] * fX[iTime] - zcorr;
 525
 526                 // build condition and process clusters
 527                 cond[0] = yexp[iTime] - kroady; cond[1] = yexp[iTime] + kroady;
 528                 cond[2] = zexp[iTime] - kroadz; cond[3] = zexp[iTime] + kroadz;
 529                 layer->GetClusters(cond, index, ncl);
 530                 for(Int_t ic = 0; ic<ncl; ic++){
 531                         AliTRDcluster *c = layer->GetCluster(index[ic]);
 532                         clusters[nYclusters] = c;
 533                         yres[nYclusters++] = c->GetY() - yexp[iTime];
 534                         if(nYclusters >= kClusterCandidates) {
 535                                 AliWarning(Form("Cluster candidates reached limit %d. Some may be lost.", kClusterCandidates));
 536                                 kEXIT = kTRUE;
 537                                 break;
 538                         }
 539                 }
 540                 tboundary[iTime] = nYclusters;
 541                 if(kEXIT) break;
 542         }
 543
 544         // Evaluate truncated mean on the y direction
 545         Double_t mean, sigma;
 546         AliMathBase::EvaluateUni(nYclusters, yres, mean, sigma, Int_t(nYclusters*.8)-2);
 547         // purge cluster candidates
 548         Int_t nZclusters = 0;
 549         for(Int_t ic = 0; ic<nYclusters; ic++){
 550                 if(yres[ic] - mean > 4. * sigma){
 551                         clusters[ic] = 0x0;
 552                         continue;
 553                 }
 554                 zres[nZclusters++] = clusters[ic]->GetZ() - zexp[clusters[ic]->GetLocalTimeBin()];
 555         }
 556
 557         // Evaluate truncated mean on the z direction
 558         AliMathBase::EvaluateUni(nZclusters, zres, mean, sigma, Int_t(nZclusters*.8)-2);
 559         // purge cluster candidates
 560         for(Int_t ic = 0; ic<nZclusters; ic++){
 561                 if(zres[ic] - mean > 4. * sigma){
 562                         clusters[ic] = 0x0;
 563                         continue;
 564                 }
 565         }
 566
 567
 568         // Select only one cluster/TimeBin
 569         Int_t lastCluster = 0;
 570         fN2 = 0;
 571         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 572                 ncl = tboundary[iTime] - lastCluster;
 573                 if(!ncl) continue;
 574                 Int_t iptr = lastCluster;
 575                 if(ncl > 1){
 576                         Float_t dold = 9999.;
 577                         for(int ic=lastCluster; ic<tboundary[iTime]; ic++){
 578                                 if(!clusters[ic]) continue;
 579                                 Float_t y = yexp[iTime] - clusters[ic]->GetY();
 580                                 Float_t z = zexp[iTime] - clusters[ic]->GetZ();
 581                                 Float_t d = y * y + z * z;
 582                                 if(d > dold) continue;
 583                                 dold = d;
 584                                 iptr = ic;
 585                         }
 586                 }
 587                 fIndexes[iTime]  = chamber->GetTB(iTime)->GetGlobalIndex(iptr);
 588                 fClusters[iTime] = clusters[iptr];
 589                 fY[iTime]        = clusters[iptr]->GetY();
 590                 fZ[iTime]        = clusters[iptr]->GetZ();
 591                 lastCluster      = tboundary[iTime];
 592                 fN2++;
 593         }
 594
 595         // number of minimum numbers of clusters expected for the tracklet
 596         Int_t kClmin = Int_t(AliTRDReconstructor::RecoParam()->GetFindableClusters()*AliTRDtrackerV1::GetNTimeBins());
 597   if (fN2 < kClmin){
 598                 AliWarning(Form("Not enough clusters to fit the tracklet %d [%d].", fN2, kClmin));
 599     fN2 = 0;
 600     return kFALSE;
 601   }
 602
 603         // update used clusters
 604         fNUsed = 0;
 605         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 606                 if(!fClusters[iTime]) continue;
 607                 if((fClusters[iTime]->IsUsed())) fNUsed++;
 608         }
 609
 610   if (fN2-fNUsed < kClmin){
 611                 AliWarning(Form("Too many clusters already in use %d (from %d).", fNUsed, fN2));
 612     fN2 = 0;
 613     return kFALSE;
 614   }
 615
 616         return kTRUE;
 617 }
 618
 619 //____________________________________________________________________
 620 Bool_t AliTRDseedV1::Fit()
 621 {
 622   //
 623   // Linear fit of the tracklet
 624   //
 625   // Parameters :
 626   //
 627   // Output :
 628   //  True if successful
 629   //
 630   // Detailed description
 631   // 2. Check if tracklet crosses pad row boundary
 632   // 1. Calculate residuals in the y (r-phi) direction
 633   // 3. Do a Least Square Fit to the data
 634   //
 635
 636         const Int_t kClmin = 8;
 637         const Int_t kNtb = AliTRDtrackerV1::GetNTimeBins();
 638         AliTRDtrackerV1::AliTRDLeastSquare fitterY, fitterZ;
 639
 640         // convertion factor from square to gauss distribution for sigma
 641         Double_t convert = 1./TMath::Sqrt(12.);
 642
 643         // book cluster information
 644         Double_t xc[knTimebins+1], yc[knTimebins], zc[knTimebins+1], sy[knTimebins], sz[knTimebins+1];
 645         Int_t zRow[knTimebins];
 646         AliTRDcluster *c = 0x0;
 647         Int_t nc = 0;
 648         for (Int_t ic=0; ic<kNtb; ic++) {
 649                 zRow[ic] = -1;
 650                 xc[ic]  = -1.;
 651                 yc[ic]  = 999.;
 652                 zc[ic]  = 999.;
 653                 sy[ic]  = 0.;
 654                 sz[ic]  = 0.;
 655                 if(!(c = fClusters[ic])) continue;
 656                 if(!c->IsInChamber()) continue;
 657                 Float_t w = 1.;
 658                 if(c->GetNPads()>4) w = .5;
 659                 if(c->GetNPads()>5) w = .2;
 660                 zRow[nc] = c->GetPadRow();
 661                 xc[nc]   = fX0 - c->GetX();
 662                 yc[nc]   = c->GetY();
 663                 zc[nc]   = c->GetZ();
 664                 sy[ic]   = w; // all clusters have the same sigma
 665                 sz[ic]   = fPadLength*convert;
 666                 fitterZ.AddPoint(&xc[ic], zc[ic], sz[ic]);
 667                 nc++;
 668         }
 669   // to few clusters
 670         if (nc < kClmin) return kFALSE;
 671
 672
 673         Int_t zN[2*35];
 674   Int_t nz = AliTRDtrackerV1::Freq(nc, zRow, zN, kFALSE);
 675         // more than one pad row crossing
 676         if(nz>2) return kFALSE;
 677
 678         // estimate reference parameter at average x
 679         Double_t y0 = fYref[0];
 680         Double_t dydx = fYref[1];
 681         Double_t dzdx = fZref[1];
 682         zc[nc]  = fZref[0];
 683
 684         // determine z offset of the fit
 685         Int_t nchanges = 0, nCross = 0;
 686         if(nz==2){ // tracklet is crossing pad row
 687                 // Find the break time allowing one chage on pad-rows
 688                 // with maximal number of accepted clusters
 689                 Int_t padRef = zRow[0];
 690                 for (Int_t ic=1; ic<nc; ic++) {
 691                         if(zRow[ic] == padRef) continue;
 692
 693                         // debug
 694                         if(zRow[ic-1] == zRow[ic]){
 695                                 printf("ERROR in pad row change!!!\n");
 696                         }
 697
 698                         // evaluate parameters of the crossing point
 699                         Float_t sx = (xc[ic-1] - xc[ic])*convert;
 700                         xc[nc] = .5 * (xc[ic-1] + xc[ic]);
 701                         zc[nc] = .5 * (zc[ic-1] + zc[ic]);
 702                         sz[nc] = TMath::Max(dzdx * sx, .01);
 703                         dzdx   = zc[ic-1] > zc[ic] ? 1. : -1.;
 704                         padRef = zRow[ic];
 705                         nCross = ic;
 706                         nchanges++;
 707                 }
 708         }
 709
 710         // condition on nCross and reset nchanges TODO
 711
 712         if(nchanges==1){
 713                 if(dzdx * fZref[1] < 0.){
 714                         AliInfo("tracklet direction does not correspond to the track direction. TODO.");
 715                 }
 716                 SetBit(2, kTRUE); // mark pad row crossing
 717                 fCross[0] = xc[nc]; fCross[2] = zc[nc]; fCross[3] = sz[nc];
 718                 fitterZ.AddPoint(&xc[nc], zc[nc], sz[nc]);
 719                 fitterZ.Eval();
 720                 dzdx = fZref[1]; // we don't trust Parameter[1] ??;
 721                 zc[nc] = fitterZ.GetFunctionParameter(0);
 722         } else if(nchanges > 1){ // debug
 723                 AliInfo("ERROR in n changes!!!");
 724                 return kFALSE;
 725         }
 726
 727
 728         // estimate deviation from reference direction
 729         dzdx *= fTilt;
 730         for (Int_t ic=0; ic<nc; ic++) {
 731                 yc[ic] -= y0 + xc[ic]*(dydx + dzdx) + fTilt * (zc[ic] - zc[nc]);
 732                 fitterY.AddPoint(&xc[ic], yc[ic], sy[ic]);
 733         }
 734         fitterY.Eval();
 735         fYfit[0] = y0+fitterY.GetFunctionParameter(0);
 736         fYfit[1] = dydx+fitterY.GetFunctionParameter(1);
 737         if(nchanges) fCross[1] = fYfit[0] + fCross[0] * fYfit[1];
 738
 739 //      printf("\nnz = %d\n", nz);
 740 //      for(int ic=0; ic<35; ic++) printf("%d row[%d]\n", ic, zRow[ic]);
 741 //
 742 //      for(int ic=0; ic<nz; ic++) printf("%d n[%d]\n", ic, zN[ic]);
 743
 744         return kTRUE;
 745 }
 746
 747 //___________________________________________________________________
 748 void AliTRDseedV1::Draw(Option_t*)
 749 {
 750 }
 751
 752 //___________________________________________________________________
 753 void AliTRDseedV1::Print(Option_t*) const
 754 {
 755   //
 756   // Printing the seedstatus
 757   //
 758
 759         printf("Seed status :\n");
 760         printf("  fTilt      = %f\n", fTilt);
 761         printf("  fPadLength = %f\n", fPadLength);
 762         printf("  fX0        = %f\n", fX0);
 763         for(int ic=0; ic<AliTRDtrackerV1::GetNTimeBins(); ic++) {
 764           const Char_t *isUsable = fUsable[ic]?"Yes":"No";
 765           printf("  %d X[%f] Y[%f] Z[%f] Indexes[%d] clusters[%p] usable[%s]\n"
 766                 , ic
 767                 , fX[ic]
 768                 , fY[ic]
 769                 , fZ[ic]
 770                 , fIndexes[ic]
 771                 , ((void*) fClusters[ic])
 772                 , isUsable);
 773         }
 774
 775         printf("  fYref[0] =%f fYref[1] =%f\n", fYref[0], fYref[1]);
 776         printf("  fZref[0] =%f fZref[1] =%f\n", fZref[0], fZref[1]);
 777         printf("  fYfit[0] =%f fYfit[1] =%f\n", fYfit[0], fYfit[1]);
 778         printf("  fYfitR[0]=%f fYfitR[1]=%f\n", fYfitR[0], fYfitR[1]);
 779         printf("  fZfit[0] =%f fZfit[1] =%f\n", fZfit[0], fZfit[1]);
 780         printf("  fZfitR[0]=%f fZfitR[1]=%f\n", fZfitR[0], fZfitR[1]);
 781         printf("  fSigmaY =%f\n", fSigmaY);
 782         printf("  fSigmaY2=%f\n", fSigmaY2);
 783         printf("  fMeanz  =%f\n", fMeanz);
 784         printf("  fZProb  =%f\n", fZProb);
 785         printf("  fLabels[0]=%d fLabels[1]=%d\n", fLabels[0], fLabels[1]);
 786         printf("  fN      =%d\n", fN);
 787         printf("  fN2     =%d (>8 isOK)\n",fN2);
 788         printf("  fNUsed  =%d\n", fNUsed);
 789         printf("  fFreq   =%d\n", fFreq);
 790         printf("  fNChange=%d\n",  fNChange);
 791         printf("  fMPads  =%f\n", fMPads);
 792
 793         printf("  fC      =%f\n", fC);
 794         printf("  fCC     =%f\n",fCC);
 795         printf("  fChi2   =%f\n", fChi2);
 796         printf("  fChi2Z  =%f\n", fChi2Z);
 797 }
 798