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 "AliTRDcluster.h"
  37 #include "AliTRDseedV1.h"
  38 #include "AliTRDtrackV1.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 Bool_t AliTRDseedV1::Init(AliTRDtrackV1 *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         if(!track->GetProlongation(fX0, y, z)) return kFALSE;
 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         return kTRUE;
 167 }
 168
 169
 170 //____________________________________________________________________
 171 void AliTRDseedV1::CookdEdx(Int_t nslices)
 172 {
 173 // Calculates average dE/dx for all slices and store them in the internal array fdEdx.
 174 //
 175 // Parameters:
 176 //  nslices : number of slices for which dE/dx should be calculated
 177 // Output:
 178 //  store results in the internal array fdEdx. This can be accessed with the method
 179 //  AliTRDseedV1::GetdEdx()
 180 //
 181 // Detailed description
 182 // Calculates average dE/dx for all slices. Depending on the PID methode
 183 // the number of slices can be 3 (LQ) or 8(NN).
 184 // The calculation of dQ/dl are done using the tracklet fit results (see AliTRDseedV1::GetdQdl(Int_t)) i.e.
 185 //
 186 // dQ/dl = qc/(dx * sqrt(1 + dy/dx^2 + dz/dx^2))
 187 //
 188 // The following effects are included in the calculation:
 189 // 1. calibration values for t0 and vdrift (using x coordinate to calculate slice)
 190 // 2. cluster sharing (optional see AliTRDrecoParam::SetClusterSharing())
 191 // 3. cluster size
 192 //
 193
 194         Int_t nclusters[knSlices];
 195         for(int i=0; i<knSlices; i++){
 196                 fdEdx[i]     = 0.;
 197                 nclusters[i] = 0;
 198         }
 199         Float_t clength = (/*.5 * */AliTRDgeometry::AmThick() + AliTRDgeometry::DrThick());
 200
 201         AliTRDcluster *cluster = 0x0;
 202         for(int ic=0; ic<AliTRDtrackerV1::GetNTimeBins(); ic++){
 203                 if(!(cluster = fClusters[ic])) continue;
 204                 Float_t x = cluster->GetX();
 205
 206                 // Filter clusters for dE/dx calculation
 207
 208                 // 1.consider calibration effects for slice determination
 209                 Int_t slice;
 210                 if(cluster->IsInChamber()) slice = Int_t(TMath::Abs(fX0 - x) * nslices / clength);
 211                 else slice = x < fX0 ? 0 : nslices-1;
 212
 213                 // 2. take sharing into account
 214                 Float_t w = cluster->IsShared() ? .5 : 1.;
 215
 216                 // 3. take into account large clusters TODO
 217                 //w *= c->GetNPads() > 3 ? .8 : 1.;
 218
 219                 //CHECK !!!
 220                 fdEdx[slice]   += w * GetdQdl(ic); //fdQdl[ic];
 221                 nclusters[slice]++;
 222         } // End of loop over clusters
 223
 224         if(AliTRDReconstructor::RecoParam()->GetPIDMethod() == 0){
 225         // calculate mean charge per slice (only LQ PID)
 226                 for(int is=0; is<nslices; is++){
 227             if(nclusters[is]) fdEdx[is] /= nclusters[is];
 228           }
 229         }
 230 }
 231
 232
 233 //____________________________________________________________________
 234 Float_t AliTRDseedV1::GetdQdl(Int_t ic) const
 235 {
 236         return fClusters[ic] ? TMath::Abs(fClusters[ic]->GetQ()) /fdX / TMath::Sqrt(1. + fYfit[1]*fYfit[1] + fZref[1]*fZref[1]) : 0.;
 237 }
 238
 239 //____________________________________________________________________
 240 Double_t* AliTRDseedV1::GetProbability()
 241 {
 242 // Fill probability array for tracklet from the DB.
 243 //
 244 // Parameters
 245 //
 246 // Output
 247 //   returns pointer to the probability array and 0x0 if missing DB access
 248 //
 249 // Detailed description
 250
 251
 252         // retrive calibration db
 253   AliTRDcalibDB *calibration = AliTRDcalibDB::Instance();
 254   if (!calibration) {
 255     AliError("No access to calibration data");
 256     return 0x0;
 257   }
 258
 259   // Retrieve the CDB container class with the parametric detector response
 260   const AliTRDCalPID *pd = calibration->GetPIDObject(AliTRDReconstructor::RecoParam()->GetPIDMethod());
 261   if (!pd) {
 262     AliError("No access to AliTRDCalPID object");
 263     return 0x0;
 264   }
 265         //AliInfo(Form("Method[%d] : %s", AliTRDReconstructor::RecoParam()->GetPIDMethod(), pd->IsA()->GetName()));
 266
 267         // calculate tracklet length TO DO
 268   Float_t length = (AliTRDgeometry::AmThick() + AliTRDgeometry::DrThick());
 269   /// TMath::Sqrt((1.0 - fSnp[iPlane]*fSnp[iPlane]) / (1.0 + fTgl[iPlane]*fTgl[iPlane]));
 270
 271   //calculate dE/dx
 272   CookdEdx(AliTRDReconstructor::RecoParam()->GetNdEdxSlices());
 273
 274   // Sets the a priori probabilities
 275   for(int ispec=0; ispec<AliPID::kSPECIES; ispec++) {
 276     fProb[ispec] = pd->GetProbability(ispec, fMom, &fdEdx[0], length, fPlane);
 277   }
 278
 279         return &fProb[0];
 280 }
 281
 282 //____________________________________________________________________
 283 Float_t AliTRDseedV1::GetQuality(Bool_t kZcorr) const
 284 {
 285   //
 286   // Returns a quality measurement of the current seed
 287   //
 288
 289         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 290         return
 291                   .5 * TMath::Abs(18.0 - fN2)
 292                 + 10.* TMath::Abs(fYfit[1] - fYref[1])
 293                 + 5. * TMath::Abs(fYfit[0] - fYref[0] + zcorr)
 294                 + 2. * TMath::Abs(fMeanz - fZref[0]) / fPadLength;
 295 }
 296
 297 //____________________________________________________________________
 298 void AliTRDseedV1::GetCovAt(Double_t /*x*/, Double_t *cov) const
 299 {
 300 // Computes covariance in the y-z plane at radial point x
 301
 302         Int_t ic = 0; while (!fClusters[ic]) ic++;
 303   AliTRDcalibDB *fCalib = AliTRDcalibDB::Instance();
 304         Double_t exB         = fCalib->GetOmegaTau(fCalib->GetVdriftAverage(fClusters[ic]->GetDetector()), -AliTracker::GetBz()*0.1);
 305
 306         Double_t sy2    = fSigmaY2*fSigmaY2 + .2*(fYfit[1]-exB)*(fYfit[1]-exB);
 307         Double_t sz2    = fPadLength/12.;
 308
 309
 310         //printf("Yfit[1] %f sy20 %f SigmaY2 %f\n", fYfit[1], sy20, fSigmaY2);
 311
 312         cov[0] = sy2;
 313         cov[1] = fTilt*(sy2-sz2);
 314         cov[2] = sz2;
 315 }
 316
 317
 318 //____________________________________________________________________
 319 void AliTRDseedV1::SetOwner(Bool_t own)
 320 {
 321         //AliInfo(Form("own [%s] fOwner[%s]", own?"YES":"NO", fOwner?"YES":"NO"));
 322
 323         if(own){
 324                 for(int ic=0; ic<knTimebins; ic++){
 325                         if(!fClusters[ic]) continue;
 326                         fClusters[ic] = new AliTRDcluster(*fClusters[ic]);
 327                 }
 328                 SetBit(1);
 329         } else {
 330                 if(IsOwner()){
 331                         for(int ic=0; ic<knTimebins; ic++){
 332                                 if(!fClusters[ic]) continue;
 333                                 delete fClusters[ic];
 334                                 //fClusters[ic] = tracker->GetClusters(index) TODO
 335                         }
 336                 }
 337                 SetBit(1, kFALSE);
 338         }
 339 }
 340
 341 //____________________________________________________________________
 342 Bool_t  AliTRDseedV1::AttachClustersIter(AliTRDtrackingChamber *chamber, Float_t quality, Bool_t kZcorr, AliTRDcluster *c)
 343 {
 344   //
 345   // Iterative process to register clusters to the seed.
 346   // In iteration 0 we try only one pad-row and if quality not
 347   // sufficient we try 2 pad-rows (about 5% of tracks cross 2 pad-rows)
 348   //
 349         // debug level 7
 350         //
 351
 352         if(!AliTRDReconstructor::RecoParam()){
 353                 AliError("Seed can not be used without a valid RecoParam.");
 354                 return kFALSE;
 355         }
 356
 357         AliTRDchamberTimeBin *layer = 0x0;
 358         if(AliTRDReconstructor::StreamLevel()>=7 && c){
 359                 TClonesArray clusters("AliTRDcluster", 24);
 360                 clusters.SetOwner(kTRUE);
 361                 AliTRDcluster *cc = 0x0;
 362                 Int_t det=-1, ncl, ncls = 0;
 363                 for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 364                         if(!(layer = chamber->GetTB(iTime))) continue;
 365                         if(!(ncl = Int_t(*layer))) continue;
 366                         for(int ic=0; ic<ncl; ic++){
 367                                 cc = (*layer)[ic];
 368                                 det = cc->GetDetector();
 369                                 new(clusters[ncls++]) AliTRDcluster(*cc);
 370                         }
 371                 }
 372                 AliInfo(Form("N clusters[%d] = %d", fPlane, ncls));
 373
 374                 Int_t ref = c ? 1 : 0;
 375                 TTreeSRedirector &cstreamer = *AliTRDtrackerV1::DebugStreamer();
 376                 cstreamer << "AttachClustersIter"
 377                         << "det="        << det
 378                         << "ref="        << ref
 379                         << "clusters.="  << &clusters
 380                         << "tracklet.="  << this
 381                         << "cl.="        << c
 382                         << "\n";
 383         }
 384
 385         Float_t  tquality;
 386         Double_t kroady = AliTRDReconstructor::RecoParam()->GetRoad1y();
 387         Double_t kroadz = fPadLength * .5 + 1.;
 388
 389         // initialize configuration parameters
 390         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 391         Int_t   niter = kZcorr ? 1 : 2;
 392
 393         Double_t yexp, zexp;
 394         Int_t ncl = 0;
 395         // start seed update
 396         for (Int_t iter = 0; iter < niter; iter++) {
 397                 ncl = 0;
 398                 for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 399                         if(!(layer = chamber->GetTB(iTime))) continue;
 400                         if(!Int_t(*layer)) continue;
 401
 402                         // define searching configuration
 403                         Double_t dxlayer = layer->GetX() - fX0;
 404                         if(c){
 405                                 zexp = c->GetZ();
 406                                 //Try 2 pad-rows in second iteration
 407                                 if (iter > 0) {
 408                                         zexp = fZref[0] + fZref[1] * dxlayer - zcorr;
 409                                         if (zexp > c->GetZ()) zexp = c->GetZ() + fPadLength*0.5;
 410                                         if (zexp < c->GetZ()) zexp = c->GetZ() - fPadLength*0.5;
 411                                 }
 412                         } else zexp = fZref[0] + (kZcorr ? fZref[1] * dxlayer : 0.);
 413                         yexp  = fYref[0] + fYref[1] * dxlayer - zcorr;
 414
 415                         // Get and register cluster
 416                         Int_t    index = layer->SearchNearestCluster(yexp, zexp, kroady, kroadz);
 417                         if (index < 0) continue;
 418                         AliTRDcluster *cl = (*layer)[index];
 419
 420                         fIndexes[iTime]  = layer->GetGlobalIndex(index);
 421                         fClusters[iTime] = cl;
 422                         fY[iTime]        = cl->GetY();
 423                         fZ[iTime]        = cl->GetZ();
 424                         ncl++;
 425                 }
 426         if(AliTRDReconstructor::StreamLevel()>=7) AliInfo(Form("iter = %d ncl [%d] = %d", iter, fPlane, ncl));
 427
 428                 if(ncl>1){
 429                         // calculate length of the time bin (calibration aware)
 430                         Int_t irp = 0; Float_t x[2]; Int_t tb[2];
 431                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 432                                 if(!fClusters[iTime]) continue;
 433                                 x[irp]  = fClusters[iTime]->GetX();
 434                                 tb[irp] = iTime;
 435                                 irp++;
 436                                 if(irp==2) break;
 437                         }
 438                         fdX = (x[1] - x[0]) / (tb[0] - tb[1]);
 439
 440                         // update X0 from the clusters (calibration/alignment aware)
 441                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 442                                 if(!(layer = chamber->GetTB(iTime))) continue;
 443                                 if(!layer->IsT0()) continue;
 444                                 if(fClusters[iTime]){
 445                                         fX0 = fClusters[iTime]->GetX();
 446                                         break;
 447                                 } else { // we have to infere the position of the anode wire from the other clusters
 448                                         for (Int_t jTime = iTime+1; jTime < AliTRDtrackerV1::GetNTimeBins(); jTime++) {
 449                                                 if(!fClusters[jTime]) continue;
 450                                                 fX0 = fClusters[jTime]->GetX() + fdX * (jTime - iTime);
 451                                         }
 452                                         break;
 453                                 }
 454                         }
 455
 456                         // update YZ reference point
 457                         // TODO
 458
 459                         // update x reference positions (calibration/alignment aware)
 460                         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 461                                 if(!fClusters[iTime]) continue;
 462                                 fX[iTime] = fClusters[iTime]->GetX() - fX0;
 463                         }
 464
 465                         AliTRDseed::Update();
 466                 }
 467         if(AliTRDReconstructor::StreamLevel()>=7) AliInfo(Form("iter = %d nclFit [%d] = %d", iter, fPlane, fN2));
 468
 469                 if(IsOK()){
 470                         tquality = GetQuality(kZcorr);
 471                         if(tquality < quality) break;
 472                         else quality = tquality;
 473                 }
 474                 kroadz *= 2.;
 475         } // Loop: iter
 476         if (!IsOK()) return kFALSE;
 477
 478         CookLabels();
 479         UpdateUsed();
 480         return kTRUE;
 481 }
 482
 483 //____________________________________________________________________
 484 Bool_t  AliTRDseedV1::AttachClusters(AliTRDtrackingChamber *chamber
 485                                        ,Bool_t kZcorr)
 486 {
 487   //
 488   // Projective algorithm to attach clusters to seeding tracklets
 489   //
 490   // Parameters
 491   //
 492   // Output
 493   //
 494   // Detailed description
 495   // 1. Collapse x coordinate for the full detector plane
 496   // 2. truncated mean on y (r-phi) direction
 497   // 3. purge clusters
 498   // 4. truncated mean on z direction
 499   // 5. purge clusters
 500   // 6. fit tracklet
 501   //
 502
 503         if(!AliTRDReconstructor::RecoParam()){
 504                 AliError("Seed can not be used without a valid RecoParam.");
 505                 return kFALSE;
 506         }
 507
 508         const Int_t kClusterCandidates = 2 * knTimebins;
 509
 510         //define roads
 511         Double_t kroady = AliTRDReconstructor::RecoParam()->GetRoad1y();
 512         Double_t kroadz = fPadLength * 1.5 + 1.;
 513         // correction to y for the tilting angle
 514         Float_t zcorr = kZcorr ? fTilt * (fZProb - fZref[0]) : 0.;
 515
 516         // working variables
 517         AliTRDcluster *clusters[kClusterCandidates];
 518         Double_t cond[4], yexp[knTimebins], zexp[knTimebins],
 519                 yres[kClusterCandidates], zres[kClusterCandidates];
 520         Int_t ncl, *index = 0x0, tboundary[knTimebins];
 521
 522         // Do cluster projection
 523         AliTRDchamberTimeBin *layer = 0x0;
 524         Int_t nYclusters = 0; Bool_t kEXIT = kFALSE;
 525         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 526                 if(!(layer = chamber->GetTB(iTime))) continue;
 527                 if(!Int_t(*layer)) continue;
 528
 529                 fX[iTime] = layer->GetX() - fX0;
 530                 zexp[iTime] = fZref[0] + fZref[1] * fX[iTime];
 531                 yexp[iTime] = fYref[0] + fYref[1] * fX[iTime] - zcorr;
 532
 533                 // build condition and process clusters
 534                 cond[0] = yexp[iTime] - kroady; cond[1] = yexp[iTime] + kroady;
 535                 cond[2] = zexp[iTime] - kroadz; cond[3] = zexp[iTime] + kroadz;
 536                 layer->GetClusters(cond, index, ncl);
 537                 for(Int_t ic = 0; ic<ncl; ic++){
 538                         AliTRDcluster *c = layer->GetCluster(index[ic]);
 539                         clusters[nYclusters] = c;
 540                         yres[nYclusters++] = c->GetY() - yexp[iTime];
 541                         if(nYclusters >= kClusterCandidates) {
 542                                 AliWarning(Form("Cluster candidates reached limit %d. Some may be lost.", kClusterCandidates));
 543                                 kEXIT = kTRUE;
 544                                 break;
 545                         }
 546                 }
 547                 tboundary[iTime] = nYclusters;
 548                 if(kEXIT) break;
 549         }
 550
 551         // Evaluate truncated mean on the y direction
 552         Double_t mean, sigma;
 553         AliMathBase::EvaluateUni(nYclusters, yres, mean, sigma, Int_t(nYclusters*.8)-2);
 554         // purge cluster candidates
 555         Int_t nZclusters = 0;
 556         for(Int_t ic = 0; ic<nYclusters; ic++){
 557                 if(yres[ic] - mean > 4. * sigma){
 558                         clusters[ic] = 0x0;
 559                         continue;
 560                 }
 561                 zres[nZclusters++] = clusters[ic]->GetZ() - zexp[clusters[ic]->GetLocalTimeBin()];
 562         }
 563
 564         // Evaluate truncated mean on the z direction
 565         AliMathBase::EvaluateUni(nZclusters, zres, mean, sigma, Int_t(nZclusters*.8)-2);
 566         // purge cluster candidates
 567         for(Int_t ic = 0; ic<nZclusters; ic++){
 568                 if(zres[ic] - mean > 4. * sigma){
 569                         clusters[ic] = 0x0;
 570                         continue;
 571                 }
 572         }
 573
 574
 575         // Select only one cluster/TimeBin
 576         Int_t lastCluster = 0;
 577         fN2 = 0;
 578         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 579                 ncl = tboundary[iTime] - lastCluster;
 580                 if(!ncl) continue;
 581                 Int_t iptr = lastCluster;
 582                 if(ncl > 1){
 583                         Float_t dold = 9999.;
 584                         for(int ic=lastCluster; ic<tboundary[iTime]; ic++){
 585                                 if(!clusters[ic]) continue;
 586                                 Float_t y = yexp[iTime] - clusters[ic]->GetY();
 587                                 Float_t z = zexp[iTime] - clusters[ic]->GetZ();
 588                                 Float_t d = y * y + z * z;
 589                                 if(d > dold) continue;
 590                                 dold = d;
 591                                 iptr = ic;
 592                         }
 593                 }
 594                 fIndexes[iTime]  = chamber->GetTB(iTime)->GetGlobalIndex(iptr);
 595                 fClusters[iTime] = clusters[iptr];
 596                 fY[iTime]        = clusters[iptr]->GetY();
 597                 fZ[iTime]        = clusters[iptr]->GetZ();
 598                 lastCluster      = tboundary[iTime];
 599                 fN2++;
 600         }
 601
 602         // number of minimum numbers of clusters expected for the tracklet
 603         Int_t kClmin = Int_t(AliTRDReconstructor::RecoParam()->GetFindableClusters()*AliTRDtrackerV1::GetNTimeBins());
 604   if (fN2 < kClmin){
 605                 AliWarning(Form("Not enough clusters to fit the tracklet %d [%d].", fN2, kClmin));
 606     fN2 = 0;
 607     return kFALSE;
 608   }
 609
 610         // update used clusters
 611         fNUsed = 0;
 612         for (Int_t iTime = 0; iTime < AliTRDtrackerV1::GetNTimeBins(); iTime++) {
 613                 if(!fClusters[iTime]) continue;
 614                 if((fClusters[iTime]->IsUsed())) fNUsed++;
 615         }
 616
 617   if (fN2-fNUsed < kClmin){
 618                 AliWarning(Form("Too many clusters already in use %d (from %d).", fNUsed, fN2));
 619     fN2 = 0;
 620     return kFALSE;
 621   }
 622
 623         return kTRUE;
 624 }
 625
 626 //____________________________________________________________________
 627 Bool_t AliTRDseedV1::Fit()
 628 {
 629   //
 630   // Linear fit of the tracklet
 631   //
 632   // Parameters :
 633   //
 634   // Output :
 635   //  True if successful
 636   //
 637   // Detailed description
 638   // 2. Check if tracklet crosses pad row boundary
 639   // 1. Calculate residuals in the y (r-phi) direction
 640   // 3. Do a Least Square Fit to the data
 641   //
 642
 643         const Int_t kClmin = 8;
 644         const Int_t kNtb = AliTRDtrackerV1::GetNTimeBins();
 645         AliTRDtrackerV1::AliTRDLeastSquare fitterY, fitterZ;
 646
 647         // convertion factor from square to gauss distribution for sigma
 648         Double_t convert = 1./TMath::Sqrt(12.);
 649
 650         // book cluster information
 651         Double_t xc[knTimebins+1], yc[knTimebins], zc[knTimebins+1], sy[knTimebins], sz[knTimebins+1];
 652         Int_t zRow[knTimebins];
 653         AliTRDcluster *c = 0x0;
 654         Int_t nc = 0;
 655         for (Int_t ic=0; ic<kNtb; ic++) {
 656                 zRow[ic] = -1;
 657                 xc[ic]  = -1.;
 658                 yc[ic]  = 999.;
 659                 zc[ic]  = 999.;
 660                 sy[ic]  = 0.;
 661                 sz[ic]  = 0.;
 662                 if(!(c = fClusters[ic])) continue;
 663                 if(!c->IsInChamber()) continue;
 664                 Float_t w = 1.;
 665                 if(c->GetNPads()>4) w = .5;
 666                 if(c->GetNPads()>5) w = .2;
 667                 zRow[nc] = c->GetPadRow();
 668                 xc[nc]   = fX0 - c->GetX();
 669                 yc[nc]   = c->GetY();
 670                 zc[nc]   = c->GetZ();
 671                 sy[ic]   = w; // all clusters have the same sigma
 672                 sz[ic]   = fPadLength*convert;
 673                 fitterZ.AddPoint(&xc[ic], zc[ic], sz[ic]);
 674                 nc++;
 675         }
 676   // to few clusters
 677         if (nc < kClmin) return kFALSE;
 678
 679
 680         Int_t zN[2*35];
 681   Int_t nz = AliTRDtrackerV1::Freq(nc, zRow, zN, kFALSE);
 682         // more than one pad row crossing
 683         if(nz>2) return kFALSE;
 684
 685         // estimate reference parameter at average x
 686         Double_t y0 = fYref[0];
 687         Double_t dydx = fYref[1];
 688         Double_t dzdx = fZref[1];
 689         zc[nc]  = fZref[0];
 690
 691         // determine z offset of the fit
 692         Int_t nchanges = 0, nCross = 0;
 693         if(nz==2){ // tracklet is crossing pad row
 694                 // Find the break time allowing one chage on pad-rows
 695                 // with maximal number of accepted clusters
 696                 Int_t padRef = zRow[0];
 697                 for (Int_t ic=1; ic<nc; ic++) {
 698                         if(zRow[ic] == padRef) continue;
 699
 700                         // debug
 701                         if(zRow[ic-1] == zRow[ic]){
 702                                 printf("ERROR in pad row change!!!\n");
 703                         }
 704
 705                         // evaluate parameters of the crossing point
 706                         Float_t sx = (xc[ic-1] - xc[ic])*convert;
 707                         xc[nc] = .5 * (xc[ic-1] + xc[ic]);
 708                         zc[nc] = .5 * (zc[ic-1] + zc[ic]);
 709                         sz[nc] = TMath::Max(dzdx * sx, .01);
 710                         dzdx   = zc[ic-1] > zc[ic] ? 1. : -1.;
 711                         padRef = zRow[ic];
 712                         nCross = ic;
 713                         nchanges++;
 714                 }
 715         }
 716
 717         // condition on nCross and reset nchanges TODO
 718
 719         if(nchanges==1){
 720                 if(dzdx * fZref[1] < 0.){
 721                         AliInfo("tracklet direction does not correspond to the track direction. TODO.");
 722                 }
 723                 SetBit(2, kTRUE); // mark pad row crossing
 724                 fCross[0] = xc[nc]; fCross[2] = zc[nc]; fCross[3] = sz[nc];
 725                 fitterZ.AddPoint(&xc[nc], zc[nc], sz[nc]);
 726                 fitterZ.Eval();
 727                 dzdx = fZref[1]; // we don't trust Parameter[1] ??;
 728                 zc[nc] = fitterZ.GetFunctionParameter(0);
 729         } else if(nchanges > 1){ // debug
 730                 AliInfo("ERROR in n changes!!!");
 731                 return kFALSE;
 732         }
 733
 734
 735         // estimate deviation from reference direction
 736         dzdx *= fTilt;
 737         for (Int_t ic=0; ic<nc; ic++) {
 738                 yc[ic] -= y0 + xc[ic]*(dydx + dzdx) + fTilt * (zc[ic] - zc[nc]);
 739                 fitterY.AddPoint(&xc[ic], yc[ic], sy[ic]);
 740         }
 741         fitterY.Eval();
 742         fYfit[0] = y0+fitterY.GetFunctionParameter(0);
 743         fYfit[1] = dydx+fitterY.GetFunctionParameter(1);
 744         if(nchanges) fCross[1] = fYfit[0] + fCross[0] * fYfit[1];
 745
 746 //      printf("\nnz = %d\n", nz);
 747 //      for(int ic=0; ic<35; ic++) printf("%d row[%d]\n", ic, zRow[ic]);
 748 //
 749 //      for(int ic=0; ic<nz; ic++) printf("%d n[%d]\n", ic, zN[ic]);
 750
 751         return kTRUE;
 752 }
 753
 754 //___________________________________________________________________
 755 void AliTRDseedV1::Draw(Option_t*)
 756 {
 757 }
 758
 759 //___________________________________________________________________
 760 void AliTRDseedV1::Print(Option_t*) const
 761 {
 762   //
 763   // Printing the seedstatus
 764   //
 765
 766         printf("Seed status :\n");
 767         printf("  fTilt      = %f\n", fTilt);
 768         printf("  fPadLength = %f\n", fPadLength);
 769         printf("  fX0        = %f\n", fX0);
 770         for(int ic=0; ic<AliTRDtrackerV1::GetNTimeBins(); ic++) {
 771           const Char_t *isUsable = fUsable[ic]?"Yes":"No";
 772           printf("  %d X[%f] Y[%f] Z[%f] Indexes[%d] clusters[%p] usable[%s]\n"
 773                 , ic
 774                 , fX[ic]
 775                 , fY[ic]
 776                 , fZ[ic]
 777                 , fIndexes[ic]
 778                 , ((void*) fClusters[ic])
 779                 , isUsable);
 780         }
 781
 782         printf("  fYref[0] =%f fYref[1] =%f\n", fYref[0], fYref[1]);
 783         printf("  fZref[0] =%f fZref[1] =%f\n", fZref[0], fZref[1]);
 784         printf("  fYfit[0] =%f fYfit[1] =%f\n", fYfit[0], fYfit[1]);
 785         printf("  fYfitR[0]=%f fYfitR[1]=%f\n", fYfitR[0], fYfitR[1]);
 786         printf("  fZfit[0] =%f fZfit[1] =%f\n", fZfit[0], fZfit[1]);
 787         printf("  fZfitR[0]=%f fZfitR[1]=%f\n", fZfitR[0], fZfitR[1]);
 788         printf("  fSigmaY =%f\n", fSigmaY);
 789         printf("  fSigmaY2=%f\n", fSigmaY2);
 790         printf("  fMeanz  =%f\n", fMeanz);
 791         printf("  fZProb  =%f\n", fZProb);
 792         printf("  fLabels[0]=%d fLabels[1]=%d\n", fLabels[0], fLabels[1]);
 793         printf("  fN      =%d\n", fN);
 794         printf("  fN2     =%d (>8 isOK)\n",fN2);
 795         printf("  fNUsed  =%d\n", fNUsed);
 796         printf("  fFreq   =%d\n", fFreq);
 797         printf("  fNChange=%d\n",  fNChange);
 798         printf("  fMPads  =%f\n", fMPads);
 799
 800         printf("  fC      =%f\n", fC);
 801         printf("  fCC     =%f\n",fCC);
 802         printf("  fChi2   =%f\n", fChi2);
 803         printf("  fChi2Z  =%f\n", fChi2Z);
 804 }
 805