TPC/AliTPCtrackerParam.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   *
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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 $Log$
  17 Revision 1.1  2002/02/18 09:06:54  kowal2
  18 TPC parametrization by Andrea Dainese
  19
  20 */
  21 /*************************************************************************
  22  *                                                                        *
  23  * This class builds AliTPCtrack objects from generated tracks to feed    *
  24  * ITS tracking (V2). The AliTPCtrack is built from its first hit in      *
  25  * the TPC. The track is assigned a Kalman-like covariance matrix         *
  26  * depending on its pT and pseudorapidity and track parameters are        *
  27  * smeared according this covariance matrix.                              *
  28  * Output file contains sorted tracks, ready for matching with ITS        *
  29  *                                                                        *
  30  * Test macro is: AliBarrelRec_TPCparam.C                                 *
  31  *                                                                        *
  32  *  Origin: Andrea Dainese, Padova - e-mail: andrea.dainese@pd.infn.it    *
  33  *                                                                        *
  34  **************************************************************************/
  35 #include "AliTPCtrackerParam.h"
  36 #include "alles.h"
  37 #include "AliMagF.h"
  38 #include "AliTPCtrack.h"
  39 #include "TMatrixD.h"
  40 #include "AliKalmanTrack.h"
  41
  42 ClassImp(AliTPCtrackerParam)
  43
  44 //-----------------------------------------------------------------
  45 AliTPCtrackerParam::AliTPCtrackerParam(const Int_t coll,const Double_t Bz)
  46 {
  47   fColl = coll; // collision code (0: PbPb6000)
  48   fBz = Bz;     // value of the z component of L3 field (Tesla)
  49
  50 }
  51 //-----------------------------------------------------------------
  52 AliTPCtrackerParam::~AliTPCtrackerParam()
  53 {}
  54 //-----------------------------------------------------------------
  55
  56 Int_t AliTPCtrackerParam::BuildTPCtracks(const TFile *inp, TFile *out, Int_t n)
  57 {
  58
  59   if(fColl!=0) {
  60     cerr<<"AliTPCtrackerParam::BuildTPCtracks:  Invalid collision!"<<endl<<
  61                 "Available:  0   ->   PbPb6000"<<endl; return 0;
  62   }
  63   if(fBz!=0.4) {
  64     cerr<<"AliTPCtrackerParam::BuildTPCtracks:  Invalid field!"<<endl<<
  65                 "Available:  0.4"<<endl; return 0;
  66   }
  67
  68   TFile *infile=(TFile*)inp;
  69
  70   AliKalmanTrack::SetConvConst(100/0.299792458/fBz);
  71
  72   // Get gAlice object from file
  73   if(!(gAlice=(AliRun*)infile->Get("gAlice"))) {
  74     cerr<<"gAlice has not been found on galice.root !\n";
  75     return 1;
  76   }
  77
  78   // Set random number generator seed
  79   TDatime t;
  80   gRandom->SetSeed(t.Get());
  81
  82
  83   // loop over first n events in file
  84   for(Int_t evt=0; evt<n; evt++){
  85     cerr<<"+++\n+++ Processing event "<<evt<<"\n+++\n";
  86
  87     AliTPCtrack *tpctrack=0;
  88
  89     // tree for TPC tracks
  90     Char_t tname[100];
  91     sprintf(tname,"TreeT_TPC_%d",evt);
  92     TTree *tracktree = new TTree(tname,"Tree with TPC tracks");
  93     tracktree->Branch("tracks","AliTPCtrack",&tpctrack,20000,0);
  94
  95     // array for TPC tracks
  96     TObjArray tarray(20000);
  97
  98
  99     Int_t nparticles=gAlice->GetEvent(evt);
 100
 101     Bool_t done[500000];
 102     for(Int_t l=0; l<500000; l++) { done[l]=kFALSE; }
 103
 104
 105     // Get TPC detector
 106     AliTPC *TPC=(AliTPC*)gAlice->GetDetector("TPC");
 107     Int_t ver = TPC->IsVersion();
 108     cerr<<"+++ TPC version "<<ver<<" has been found !\n";
 109     AliTPCParam *digp=(AliTPCParam*)infile->Get("75x40_100x60");
 110     if(!digp) { cerr<<"TPC parameters have not been found !\n"; return 1; }
 111     TPC->SetParam(digp);
 112
 113     // Get TreeH with hits
 114     TTree *TH=gAlice->TreeH();
 115     Int_t ntracks=(Int_t)TH->GetEntries();
 116     cerr<<"+++\n+++ Number of particles in event "<<evt<<":  "<<nparticles<<"\n+++\n+++ Number of \"primary tracks\" (entries in TreeH): "<<ntracks<<"\n+++\n\n";
 117
 118     TParticle* Part;
 119     AliTPChit* tpcHit;
 120     Double_t hPx,hPy,hPz,hPt,xg,yg,zg,xl,yl,zl;
 121     Double_t Alpha;
 122     Float_t cosAlpha,sinAlpha;
 123     Int_t label,Pdg,charge,bin;
 124     Int_t tracks=0;
 125     //Int_t N1=0,N2=0;
 126
 127     // loop over entries in TreeH
 128     for(Int_t i=0; i<ntracks; i++) {
 129       if(i%1000==0) cerr<<"  --- Processing primary track "<<i<<" of "<<ntracks<<" ---\r";
 130       TPC->ResetHits();
 131       TH->GetEvent(i);
 132       // Get FirstHit
 133       tpcHit=(AliTPChit*)TPC->FirstHit(-1);
 134       for( ; tpcHit; tpcHit=(AliTPChit*)TPC->NextHit() ) {
 135         if(tpcHit->fQ !=0.) continue;
 136         // Get particle momentum at hit
 137         hPx=tpcHit->X(); hPy=tpcHit->Y(); hPz=tpcHit->Z();
 138         hPt=TMath::Sqrt(hPx*hPx+hPy*hPy);
 139         // reject hits with Pt<mag*0.45 GeV/c
 140         if(hPt<(fBz*0.45)) continue;
 141
 142         // Get track label
 143         label=tpcHit->Track();
 144         // check if this track has already been processed
 145         if(done[label]) continue;
 146         // electric charge
 147         Part = gAlice->Particle(label);
 148         Pdg = Part->GetPdgCode();
 149         if(Pdg>200 || Pdg==-11 || Pdg==-13) { charge=1; }
 150         else if(Pdg<-200 || Pdg==11 || Pdg==13) { charge=-1; }
 151         else continue;
 152
 153
 154         if((tpcHit=(AliTPChit*)TPC->NextHit())==0) break;
 155         if(tpcHit->fQ != 0.) continue;
 156         // Get global coordinates of hit
 157         xg=tpcHit->X(); yg=tpcHit->Y(); zg=tpcHit->Z();
 158         if(TMath::Sqrt(xg*xg+yg*yg)>90.) continue;
 159
 160         // Get TPC sector, Alpha angle and local coordinates
 161         // printf("Sector %d\n",tpcHit->fSector);
 162         digp->AdjustCosSin(tpcHit->fSector,cosAlpha,sinAlpha);
 163         Alpha = TMath::ATan2(sinAlpha,cosAlpha);
 164         xl = xg*cosAlpha + yg*sinAlpha;
 165         yl =-xg*sinAlpha + yg*cosAlpha;
 166         zl = zg;
 167         //printf("Alpha %f   xl %f  yl %f  zl %f\n",Alpha,xl,yl,zl);
 168
 169         // reject tracks which are not in the TPC acceptance
 170         if(TMath::Abs(zl+(244.-xl)*hPz/hPt)>252.) continue;
 171
 172         // Get bin in pT,eta
 173         bin = GetBin(hPt,Part->Eta());
 174
 175         // Apply selection according to TPC efficiency
 176         //if(abs(Pdg)==211) N1++;
 177         if(!SelectedTrack(Pdg,hPt,Part->Eta())) continue;
 178         //if(abs(Pdg)==211) N2++;
 179
 180         // Mark track as "done"
 181         done[label]=kTRUE; tracks++;
 182
 183         // create AliTPCtrack object
 184         tpctrack = BuildTrack(Alpha,xl,yl,zl,hPx,hPy,hPz,hPt,charge,label);
 185
 186         // put track in array
 187         tarray.AddLast(tpctrack);
 188
 189       }
 190
 191     } // loop over entries in TreeH
 192
 193     TObjArray newtarray(20000);
 194
 195     // assing covariance matrixes and smear track parameters
 196     CookTracks(tarray,newtarray);
 197
 198     // sort array with TPC tracks (decreasing pT)
 199     newtarray.Sort();
 200
 201
 202     Int_t arrentr = newtarray.GetEntriesFast();
 203     //printf("\n  %d  \n\n",arrentr);
 204     for(Int_t l=0; l<arrentr; l++) {
 205       tpctrack=(AliTPCtrack*)newtarray.UncheckedAt(l);
 206       tracktree->Fill();
 207     }
 208
 209     // write the tree with tracks in the output file
 210     out->cd();
 211     tracktree->Write();
 212
 213     delete tracktree;
 214
 215     printf("\n\n+++\n+++ Number of TPC tracks: %d\n+++\n",tracks);
 216     //printf("Average Eff: %f\n",(Float_t)N2/N1);
 217
 218   } // loop on events
 219
 220   return 0;
 221 }
 222
 223 //-----------------------------------------------------------------
 224 AliTPCtrack* AliTPCtrackerParam::BuildTrack(Double_t alpha,Double_t x,
 225                                             Double_t y,Double_t z,Double_t Px,
 226                                             Double_t Py,Double_t Pz,Double_t Pt,
 227                                             Int_t ch,Int_t lab)
 228 {
 229   Double_t xref = x;
 230   Double_t xx[5],cc[15];
 231   cc[0]=cc[2]=cc[5]=cc[9]=cc[14]=10.;
 232   cc[1]=cc[3]=cc[4]=cc[6]=cc[7]=cc[8]=cc[10]=cc[11]=cc[12]=cc[13]=0.;
 233
 234   // Magnetic field
 235   TVector3 Bfield(0.,0.,fBz);
 236
 237
 238   // radius [cm] of track projection in (x,y)
 239   Double_t rho = Pt*100/0.299792458/Bfield.Z();
 240   // center of track projection in local reference frame
 241   TVector3 MomH,PosH;
 242
 243
 244   // position (local) and momentum (local) at the hit
 245   // in the bending plane (z=0)
 246   PosH.SetXYZ(x,y,0.);
 247   MomH.SetXYZ(Px*TMath::Cos(alpha)+Py*TMath::Sin(alpha),-Px*TMath::Sin(alpha)+Py*TMath::Cos(alpha),0.);
 248   TVector3 Vrho = MomH.Cross(Bfield);
 249   Vrho *= ch;
 250   Vrho.SetMag(rho);
 251
 252   TVector3 Vcenter = PosH+Vrho;
 253
 254   Double_t x0 = Vcenter.X();
 255
 256   // fX     = xref         X-coordinate of this track (reference plane)
 257   // fAlpha = Alpha        Rotation angle the local (TPC sector)
 258   // fP0    = YL           Y-coordinate of a track
 259   // fP1    = ZG           Z-coordinate of a track
 260   // fP2    = C*x0         x0 is center x in rotated frame
 261   // fP3    = Tgl          tangent of the track momentum dip angle
 262   // fP4    = C            track curvature
 263   xx[0] = y;
 264   xx[1] = z;
 265   xx[3] = Pz/Pt;
 266   xx[4] = -ch/rho;
 267   xx[2] = xx[4]*x0;
 268
 269   // create the object AliTPCtrack
 270   AliTPCtrack* track = new AliTPCtrack(0,xx,cc,xref,alpha);
 271   // set the label
 272   track->SetLabel(lab);
 273
 274   return track;
 275 }
 276
 277 //-----------------------------------------------------------------
 278 Bool_t AliTPCtrackerParam::SelectedTrack(Int_t pdg,Double_t pt,Double_t eta)
 279 {
 280   Double_t eff=0.;
 281
 282   //eff computed with | zl+(244-xl)*pz/pt | < 252
 283   Double_t effPi[27] = {0.724587,0.743389,0.619273,0.798477,0.812036,0.823195,0.771437,0.775826,0.784136,0.809071,0.762001,0.774576,0.848834,0.787201,0.792548,0.942089,0.951631,0.951085,0.960885,0.971451,0.969103,0.983245,0.978939,0.988706,0.990852,0.985679,0.993606};
 284   Double_t effK[18]  = {0.377934,0.363962,0.321721,0.518784,0.547459,0.517878,0.612704,0.619101,0.620894,0.733411,0.732128,0.750373,0.790630,0.806565,0.791353,0.967486,0.970483,0.974527};
 285   Double_t effP[15]  = {0.131173,0.165114,0.229658,0.365357,0.412989,0.483297,0.454614,0.505173,0.658615,0.694753,0.730661,0.815680,0.873461,0.887227,0.899324};
 286   Double_t effEl[15] = {0.835549,0.853746,0.718207,0.835230,0.831489,0.862222,0.757783,0.747301,0.824096,0.867949,0.871891,0.808480,0.890625,0.911765,0.973684};
 287   Double_t effMu[15] = {0.553486,0.641392,0.609932,0.591126,0.706729,0.750755,0.747952,0.729051,0.760849,0.898810,0.737500,0.830357,0.735294,0.800000,0.882353};
 288
 289
 290   if(TMath::Abs(pdg)==211)  eff = LinearInterpolation(9,effPi,pt,eta);
 291   if(TMath::Abs(pdg)==321)  eff = LinearInterpolation(6,effK,pt,eta);
 292   if(TMath::Abs(pdg)==2212) eff = LinearInterpolation(5,effP,pt,eta);
 293   if(TMath::Abs(pdg)==11)   eff = LinearInterpolation(5,effEl,pt,eta);
 294   if(TMath::Abs(pdg)==13)   eff = LinearInterpolation(5,effMu,pt,eta);
 295
 296   if(gRandom->Rndm() < eff) return kTRUE;
 297
 298   return kFALSE;
 299 }
 300
 301 //-----------------------------------------------------------------
 302 Double_t AliTPCtrackerParam::LinearInterpolation(Int_t ptBins,Double_t *value,
 303                                                  Double_t pt,Double_t eta)
 304 {
 305   Double_t kValue=0,kValue1=0,kValue2=0;
 306   Int_t kEtaSide = (TMath::Abs(eta)<.45 ? 0 : 1);
 307   Double_t kEta[3]={0.15,0.45,0.75};
 308   Double_t kPt[9]={0.244,0.390,0.676,1.190,2.36,4.,6.,10.,20.};
 309   if(ptBins==6) kPt[5]=10.;
 310
 311   for(Int_t i=0; i<ptBins; i++) {
 312     if(pt<kPt[i]) {
 313       if(i==0) i=1;
 314       kValue1 = value[3*i-3+kEtaSide]+(value[3*i-3+kEtaSide]-value[3*i+kEtaSide])/(kPt[i-1]-kPt[i])*(pt-kPt[i-1]);
 315       kValue2 = value[3*i-3+kEtaSide+1]+(value[3*i-3+kEtaSide+1]-value[3*i+kEtaSide+1])/(kPt[i-1]-kPt[i])*(pt-kPt[i-1]);
 316
 317       kValue = kValue1+(kValue1-kValue2)/(kEta[kEtaSide]-kEta[kEtaSide+1])*(eta-kEta[kEtaSide]);
 318       break;
 319     }
 320     if(i==ptBins-1) {
 321       i=ptBins-2;
 322       kValue1 = value[3*i-3+kEtaSide]+(value[3*i-3+kEtaSide]-value[3*i+kEtaSide])/(kPt[i-1]-kPt[i])*(pt-kPt[i-1]);
 323       kValue2 = value[3*i-3+kEtaSide+1]+(value[3*i-3+kEtaSide+1]-value[3*i+kEtaSide+1])/(kPt[i-1]-kPt[i])*(pt-kPt[i-1]);
 324
 325       kValue = kValue1+(kValue1-kValue2)/(kEta[kEtaSide]-kEta[kEtaSide+1])*(eta-kEta[kEtaSide]);
 326       break;
 327     }
 328   }
 329
 330   return kValue;
 331 }
 332
 333 //-----------------------------------------------------------------
 334 Int_t AliTPCtrackerParam::GetBin(Double_t pt,Double_t eta) {
 335
 336   if(TMath::Abs(eta)<0.3) {
 337     if(pt<0.3)            return 0;
 338     if(pt>=0.3 && pt<0.5) return 3;
 339     if(pt>=0.5 && pt<1.)  return 6;
 340     if(pt>=1. && pt<1.5)  return 9;
 341     if(pt>=1.5 && pt<3.)  return 12;
 342     if(pt>=3. && pt<5.)   return 15;
 343     if(pt>=5. && pt<7.)   return 18;
 344     if(pt>=7. && pt<15.)  return 21;
 345     if(pt>=15.)           return 24;
 346   }
 347   if(TMath::Abs(eta)>=0.3 && TMath::Abs(eta)<0.6) {
 348     if(pt<0.3)            return 1;
 349     if(pt>=0.3 && pt<0.5) return 4;
 350     if(pt>=0.5 && pt<1.)  return 7;
 351     if(pt>=1. && pt<1.5)  return 10;
 352     if(pt>=1.5 && pt<3.)  return 13;
 353     if(pt>=3. && pt<5.)   return 16;
 354     if(pt>=5. && pt<7.)   return 19;
 355     if(pt>=7. && pt<15.)  return 22;
 356     if(pt>=15.)           return 25;
 357   }
 358   if(TMath::Abs(eta)>=0.6) {
 359     if(pt<0.3)            return 2;
 360     if(pt>=0.3 && pt<0.5) return 5;
 361     if(pt>=0.5 && pt<1.)  return 8;
 362     if(pt>=1. && pt<1.5)  return 11;
 363     if(pt>=1.5 && pt<3.)  return 14;
 364     if(pt>=3. && pt<5.)   return 17;
 365     if(pt>=5. && pt<7.)   return 20;
 366     if(pt>=7. && pt<15.)  return 23;
 367     if(pt>=15.)           return 26;
 368   }
 369
 370   return -1;
 371
 372 }
 373
 374 //-----------------------------------------------------------------
 375
 376 TMatrixD AliTPCtrackerParam::GetSmearingMatrix(Double_t* cc,Double_t pt,Double_t eta)
 377 {
 378   TMatrixD CovMat(5,5);
 379
 380   CovMat(0,0)=cc[0];
 381   CovMat(1,0)=cc[1];  CovMat(0,1)=CovMat(1,0);
 382   CovMat(1,1)=cc[2];
 383   CovMat(2,0)=cc[3];  CovMat(0,2)=CovMat(2,0);
 384   CovMat(2,1)=cc[4];  CovMat(1,2)=CovMat(2,1);
 385   CovMat(2,2)=cc[5];
 386   CovMat(3,0)=cc[6];  CovMat(0,3)=CovMat(3,0);
 387   CovMat(3,1)=cc[7];  CovMat(1,3)=CovMat(3,1);
 388   CovMat(3,2)=cc[8];  CovMat(2,3)=CovMat(3,2);
 389   CovMat(3,3)=cc[9];
 390   CovMat(4,0)=cc[10]; CovMat(0,4)=CovMat(4,0);
 391   CovMat(4,1)=cc[11]; CovMat(1,4)=CovMat(4,1);
 392   CovMat(4,2)=cc[12]; CovMat(2,4)=CovMat(4,2);
 393   CovMat(4,3)=cc[13]; CovMat(3,4)=CovMat(4,3);
 394   CovMat(4,4)=cc[14];
 395
 396   TMatrixD ScaleMat(5,5);
 397   for(Int_t k=0;k<5;k++) {
 398     for(Int_t l=0;l<5;l++) {
 399       ScaleMat(k,l)=0.;
 400     }
 401   }
 402
 403
 404   Double_t s00[27]={1.3553,1.2973,1.2446,1.3428,1.3031,1.2345,1.3244,1.2681,1.2046,1.3046,1.2430,1.1606,1.2462,1.2104,1.1082,1.2207,1.1189,1.0789,1.2079,1.1300,1.0426,1.1502,1.1122,1.0559,1.1419,1.1072,1.0208};
 405   Double_t s11[27]={1.0890,1.1463,1.2313,1.1149,1.1597,1.2280,1.1225,1.1584,1.2329,1.1149,1.1550,1.2369,1.1095,1.1353,1.2050,1.0649,1.0858,1.1546,1.0663,1.0672,1.1340,1.0416,1.0738,1.0945,1.0663,1.0654,1.0909};
 406   Double_t s22[27]={1.1709,1.1367,1.0932,1.2247,1.1832,1.1247,1.2470,1.2017,1.1441,1.2202,1.1653,1.1050,1.1819,1.1269,1.0583,1.1546,1.0621,0.9928,1.1305,1.0512,0.9576,1.0995,1.0445,0.9884,1.0968,1.0368,0.9574};
 407   Double_t s33[27]={0.9720,0.9869,1.0271,1.0030,1.0223,1.0479,1.0164,1.0305,1.0559,1.0339,1.0450,1.0686,1.0450,1.0507,1.0784,1.0334,1.0208,1.0863,1.0252,1.0114,1.0835,0.9854,1.0144,1.0507,1.0124,1.0159,1.0464};
 408   Double_t s44[27]={1.1104,1.0789,1.0479,1.1597,1.1234,1.0728,1.2087,1.1602,1.1041,1.1942,1.1428,1.0831,1.1572,1.1036,1.0431,1.1296,1.0498,0.9844,1.1145,1.0266,0.9489,1.0959,1.0450,0.9875,1.0775,1.0266,0.9406};
 409
 410
 411   ScaleMat(0,0) = LinearInterpolation(9,s00,pt,eta);
 412   ScaleMat(1,1) = LinearInterpolation(9,s11,pt,eta);
 413   ScaleMat(2,2) = LinearInterpolation(9,s22,pt,eta);
 414   ScaleMat(3,3) = LinearInterpolation(9,s33,pt,eta);
 415   ScaleMat(4,4) = LinearInterpolation(9,s44,pt,eta);
 416
 417   TMatrixD Mat(ScaleMat,TMatrixD::kMult,CovMat);
 418   TMatrixD CovMatSmear(Mat,TMatrixD::kMult,ScaleMat);
 419
 420
 421   return CovMatSmear;
 422 }
 423
 424 //-----------------------------------------------------------------
 425 void AliTPCtrackerParam::SmearTrack(Double_t* xx,Double_t* xxsm,TMatrixD cov) {
 426
 427   // build triangular matrix Bmat
 428   TMatrixD* Bmat = new TMatrixD(5,5);
 429
 430   for(Int_t j=0;j<5;j++){
 431     Double_t accum = 0;
 432     for(Int_t k=0;k<j;k++){
 433       accum += (*Bmat)(j,k)* (*Bmat)(j,k);
 434     }
 435     (*Bmat)(j,j)=TMath::Sqrt(TMath::Abs(cov(j,j)-accum));
 436     for(Int_t i=j+1;i<5;i++){
 437       accum = 0;
 438       for(Int_t k=0;k<j;k++){
 439         accum+=(*Bmat)(i,k)* (*Bmat)(j,k);
 440       }
 441       (*Bmat)(i,j) = (cov(i,j)-accum) / (*Bmat)(j,j);
 442     }
 443   }
 444
 445   // get array of numbers with normal distribution
 446   TArrayD norm;
 447   norm.Set(5);
 448   for(Int_t l=0;l<5;l++) {
 449     norm[l]=gRandom->Gaus();
 450   }
 451
 452   // use Bmat matrix to generate correlated numbers
 453   TArrayD corr;
 454   corr.Set(5);
 455   for(Int_t i=0;i<5;i++){
 456     corr[i]=0;
 457     for(Int_t j=0;j<=i;j++) corr[i] += (*Bmat)(i,j)*norm[j];
 458   }
 459
 460   delete Bmat;
 461
 462   for(Int_t l=0;l<5;l++) {
 463     xxsm[l] = xx[l]+corr[l];
 464   }
 465
 466   return;
 467 }
 468
 469 //-----------------------------------------------------------------
 470 void AliTPCtrackerParam::CookTracks(TObjArray& tarray,TObjArray& newtarray)
 471 {
 472   TString* s = new TString("$ALICE_ROOT/TPC/CovMatrixDB_");
 473   if(fColl==0) s->Append("PbPb6000");
 474   if(fBz==0.4) s->Append("_B0.4T.root");
 475   // open file with matrixes DB
 476   TFile* DBfile = new TFile(s->Data());
 477
 478   AliTPCtrack* track=new AliTPCtrack;
 479   Int_t entr = (Int_t)tarray.GetEntriesFast();
 480
 481   for(Int_t k=0; k<entr; k++) {
 482     track=(AliTPCtrack*)tarray.UncheckedAt(k);
 483
 484     Double_t pt = 1/TMath::Abs(track->Get1Pt());
 485     Double_t eta = -TMath::Log(TMath::Tan(0.25*TMath::Pi()-0.5*TMath::ATan(track->GetTgl())));
 486
 487     Int_t bin = GetBin(pt,eta);
 488
 489     // string with tree name
 490     TString str("Tree_bin");
 491     str+=bin;
 492
 493     // get the right tree
 494     TTree* CovTree = (TTree*)DBfile->Get(str.Data());
 495     TArrayF* matrix = new TArrayF;
 496     CovTree->SetBranchAddress("matrixes",&matrix);
 497
 498     // get random entry from the tree
 499     Int_t Entries = (Int_t)CovTree->GetEntries();
 500     CovTree->GetEvent(gRandom->Integer(Entries));
 501
 502     Double_t xref,alpha,xx[5],xxsm[5],cc[15];
 503     Int_t lab;
 504     // get P and Cosl from track
 505     Double_t Cosl = TMath::Cos(TMath::ATan(track->GetTgl()));
 506     Double_t P = 1/TMath::Abs(track->Get1Pt())/Cosl;
 507
 508     // get covariance matrix from regularized matrix
 509     cc[0]=matrix->At(0)*(1.588e-3+1.911e-4/TMath::Power(P,1.5));
 510     cc[1]=matrix->At(1);
 511     cc[2]=matrix->At(2)*(1.195e-3+0.8102e-3/P);
 512     cc[3]=matrix->At(3)*(7.275e-5+1.181e-5/TMath::Power(P,1.5));
 513     cc[4]=matrix->At(4);
 514     cc[5]=matrix->At(5)*(5.163e-6+1.138e-6/TMath::Power(P,2.)/Cosl);
 515     cc[6]=matrix->At(6);
 516     cc[7]=matrix->At(7)*(1.176e-5+1.175e-5/TMath::Power(P,1.5)/Cosl/Cosl/Cosl);
 517     cc[8]=matrix->At(8);
 518     cc[9]=matrix->At(9)*(1.289e-7+4.636e-7/TMath::Power(P,1.7)/Cosl/Cosl/Cosl/Cosl);
 519     cc[10]=matrix->At(10)*(4.056e-7+4.379e-8/TMath::Power(P,1.5));
 520     cc[11]=matrix->At(11);
 521     cc[12]=matrix->At(12)*(3.049e-8+8.244e-9/TMath::Power(P,2.)/Cosl);
 522     cc[13]=matrix->At(13);
 523     cc[14]=matrix->At(14)*(1.847e-10+5.822e-11/TMath::Power(P,2.)/Cosl/Cosl/Cosl);
 524
 525     TMatrixD CovMatSmear(5,5);
 526
 527     CovMatSmear = GetSmearingMatrix(cc,pt,eta);
 528
 529     // get track original parameters
 530     xref=track->GetX();
 531     alpha=track->GetAlpha();
 532     xx[0]=track->GetY();
 533     xx[1]=track->GetZ();
 534     xx[2]=track->GetX()*track->GetC()-track->GetSnp();
 535     xx[3]=track->GetTgl();
 536     xx[4]=track->GetC();
 537     lab=track->GetLabel();
 538
 539     // use smearing matrix to smear the original parameters
 540     SmearTrack(xx,xxsm,CovMatSmear);
 541
 542     AliTPCtrack* tpctrack = new AliTPCtrack(0,xxsm,cc,xref,alpha);
 543     tpctrack->SetLabel(lab);
 544
 545     // fill the array
 546     newtarray.AddLast(tpctrack);
 547
 548   }
 549
 550   DBfile->Close();
 551
 552   return;
 553 }
 554 //-----------------------------------------------------------------
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