small fix

[u/mrichter/AliRoot.git] / TRD / AliTRDtrack.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/* $Id$ */

#include <Riostream.h>
#include <TMath.h>
#include <TVector2.h>

#include "AliESDtrack.h"
#include "AliTRDgeometry.h" 
#include "AliTRDcluster.h" 
#include "AliTRDtrack.h"
#include "AliTRDtracklet.h"

ClassImp(AliTRDtrack)

///////////////////////////////////////////////////////////////////////////////
//                                                                           //
//  Represents a reconstructed TRD track                                     //
//  Local TRD Kalman track                                                   //
//                                                                           //
///////////////////////////////////////////////////////////////////////////////

AliTRDtrack::AliTRDtrack():
  AliKalmanTrack(),
  fSeedLab(-1),
  fdEdx(0),
  fdEdxT(0),
  fDE(0),
  fAlpha(0),
  fX(0),
  fStopped(kFALSE),
  fY(0),
  fZ(0),
  fE(0),
  fT(0),
  fC(0),
  fCyy(1e10),
  fCzy(0),
  fCzz(1e10),
  fCey(0),
  fCez(0),
  fCee(1e10),
  fCty(0),
  fCtz(0),
  fCte(0),
  fCtt(1e10),
  fCcy(0),
  fCcz(0),
  fCce(0),
  fCct(0),
  fCcc(1e10),
  fLhElectron(0),
  fNWrong(0),
  fNRotate(0),
  fNCross(0),
  fNExpected(0),
  fNLast(0),
  fNExpectedLast(0),
  fNdedx(0),
  fChi2Last(1e10),
  fBackupTrack(0x0)

{
  for (Int_t i=0; i<kNplane; i++) {
    for (Int_t j=0; j<kNslice; j++) {
      fdEdxPlane[i][j] = 0;
    }
    fTimBinPlane[i] = -1;
  }
  for (UInt_t i=0; i<kMAXCLUSTERSPERTRACK; i++) {
    fIndex[i] = 0;
    fIndexBackup[i] = 0;
    fdQdl[i] = 0;
  }
  for (Int_t i=0; i<3; i++) fBudget[i] = 0;
}

//_____________________________________________________________________________
AliTRDtrack::AliTRDtrack(const AliTRDcluster *c, UInt_t index, 
                         const Double_t xx[5], const Double_t cc[15], 
                         Double_t xref, Double_t alpha) : AliKalmanTrack() {
  //-----------------------------------------------------------------
  // This is the main track constructor.
  //-----------------------------------------------------------------

  fSeedLab = -1;

  fAlpha=alpha;
  if (fAlpha<-TMath::Pi()) fAlpha += 2*TMath::Pi();
  if (fAlpha>=TMath::Pi()) fAlpha -= 2*TMath::Pi();   

  fX=xref;

  fY=xx[0]; fZ=xx[1]; fE=xx[2]; fT=xx[3]; fC=xx[4];
 
  SaveLocalConvConst();

  fCyy=cc[0];
  fCzy=cc[1];  fCzz=cc[2];
  fCey=cc[3];  fCez=cc[4];  fCee=cc[5];
  fCty=cc[6];  fCtz=cc[7];  fCte=cc[8];  fCtt=cc[9];
  fCcy=cc[10]; fCcz=cc[11]; fCce=cc[12]; fCct=cc[13]; fCcc=cc[14];  
  
  fIndex[0]=index;
  SetNumberOfClusters(1);

  fdEdx=0.;
  fdEdxT=0.;
  fDE=0.;
  for (Int_t i=0;i<kNplane;i++){
    for (Int_t j=0; j<kNslice; j++) {
      fdEdxPlane[i][j] = 0;
    }
    fTimBinPlane[i] = -1;
  }

  fLhElectron = 0.0;
  fNWrong = 0;
  fNRotate = 0;
  fStopped = 0;
  fNCross =0;
  fNLast  =0;
  fChi2Last=0;
  fNExpected=0;
  fNExpectedLast=0;
  fNdedx=0;
  Double_t q = TMath::Abs(c->GetQ());
  Double_t s = fX*fC - fE, t=fT;
  if(s*s < 1) q *= TMath::Sqrt((1-s*s)/(1+t*t));

  fdQdl[0] = q;
  
  // initialisation [SR, GSI 18.02.2003] (i startd for 1)
  for(UInt_t i=1; i<kMAXCLUSTERSPERTRACK; i++) {
    fdQdl[i] = 0;
    fIndex[i] = 0;
    fIndexBackup[i] = 0;  //backup indexes MI    
  }
  for (Int_t i=0;i<3;i++) { fBudget[i]=0;};

  fBackupTrack = 0;  

}                              
           
//_____________________________________________________________________________
AliTRDtrack::AliTRDtrack(const AliTRDtrack& t) : AliKalmanTrack(t) 
{
  //
  // Copy constructor.
  //
  
  SetLabel(t.GetLabel());
  fSeedLab=t.GetSeedLabel();

  SetChi2(t.GetChi2());
  fdEdx=t.fdEdx;
  fdEdxT=t.fdEdxT;
  fDE=t.fDE;
  for (Int_t i=0;i<kNplane;i++){
    for (Int_t j=0; j<kNslice; j++) {
      fdEdxPlane[i][j] = t.fdEdxPlane[i][j];
    }
    fTimBinPlane[i] = t.fTimBinPlane[i];
    fTracklets[i]   = t.fTracklets[i];
  }

  fLhElectron = 0.0;
  fNWrong = t.fNWrong;
  fNRotate = t.fNRotate;
  fStopped = t.fStopped;
  fNCross  = t.fNCross;
  fNExpected = t.fNExpected;
  fNExpectedLast = t.fNExpectedLast;
  fNdedx         = t.fNdedx;
  fNLast     = t.fNLast;
  fChi2Last  = t.fChi2Last;
  fBackupTrack =0;
  fAlpha=t.fAlpha;
  fX=t.fX;


  fY=t.fY; fZ=t.fZ; fE=t.fE; fT=t.fT; fC=t.fC;

  fCyy=t.fCyy;
  fCzy=t.fCzy;  fCzz=t.fCzz;
  fCey=t.fCey;  fCez=t.fCez;  fCee=t.fCee;
  fCty=t.fCty;  fCtz=t.fCtz;  fCte=t.fCte;  fCtt=t.fCtt;
  fCcy=t.fCcy;  fCcz=t.fCcz;  fCce=t.fCce;  fCct=t.fCct;  fCcc=t.fCcc;  

  Int_t n=t.GetNumberOfClusters(); 
  SetNumberOfClusters(n);
  for (Int_t i=0; i<n; i++) {
    fIndex[i]=t.fIndex[i];
    fIndexBackup[i]=t.fIndex[i];  // MI - backup indexes
    fdQdl[i]=t.fdQdl[i];
  }

  // initialisation (i starts from n) [SR, GSI, 18.02.2003]
  for(UInt_t i=n; i<kMAXCLUSTERSPERTRACK; i++) {
    fdQdl[i] = 0;
    fIndex[i] = 0;
    fIndexBackup[i] = 0;  //MI backup indexes
  }
  for (Int_t i=0;i<6;i++){
    fTracklets[i] = t.fTracklets[i];
  }
  for (Int_t i=0;i<3;i++) { fBudget[i]=t.fBudget[i];};
}                                

//_____________________________________________________________________________
AliTRDtrack::AliTRDtrack(const AliKalmanTrack& t, Double_t alpha) 
           :AliKalmanTrack(t) 
{
  //
  // Constructor from AliTPCtrack or AliITStrack .
  //

  SetLabel(t.GetLabel());
  SetChi2(0.);
  SetMass(t.GetMass());
  SetNumberOfClusters(0);

  fdEdx=t.GetPIDsignal();
  fDE  = 0;
  for (Int_t i=0;i<kNplane;i++){
    for (Int_t j=0;j<kNslice;j++){
      fdEdxPlane[i][j] = 0.0;
    }
    fTimBinPlane[i] = -1;
  }

  fLhElectron = 0.0;
  fNWrong = 0;
  fNRotate = 0;
  fStopped = 0;
  fNExpected=0;
  fNExpectedLast=0;  
  fNdedx        =0;
  fNCross =0;
  fNLast  =0;
  fChi2Last =0;
  fBackupTrack =0;

  fAlpha = alpha;
  if      (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
  else if (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();

  Double_t x, p[5]; t.GetExternalParameters(x,p);

  fX=x;

  fY=p[0];
  fZ=p[1];
  fT=p[3]; x=GetLocalConvConst();
  fC=p[4]/x;
  fE=fC*fX - p[2];   

  //Conversion of the covariance matrix
  Double_t c[15]; t.GetExternalCovariance(c);

  c[10]/=x; c[11]/=x; c[12]/=x; c[13]/=x; c[14]/=x*x;

  Double_t c22=fX*fX*c[14] - 2*fX*c[12] + c[5];
  Double_t c32=fX*c[13] - c[8];
  Double_t c20=fX*c[10] - c[3], c21=fX*c[11] - c[4], c42=fX*c[14] - c[12];

  fCyy=c[0 ];
  fCzy=c[1 ];   fCzz=c[2 ];
  fCey=c20;     fCez=c21;     fCee=c22;
  fCty=c[6 ];   fCtz=c[7 ];   fCte=c32;   fCtt=c[9 ];
  fCcy=c[10];   fCcz=c[11];   fCce=c42;   fCct=c[13]; fCcc=c[14];  

  // Initialization [SR, GSI, 18.02.2003]
  for(UInt_t i=0; i<kMAXCLUSTERSPERTRACK; i++) {
    fdQdl[i] = 0;
    fIndex[i] = 0;
    fIndexBackup[i] = 0;  // MI backup indexes    
  }
  
  for (Int_t i=0;i<3;i++) { fBudget[i]=0;};
}              

//_____________________________________________________________________________
AliTRDtrack::AliTRDtrack(const AliESDtrack& t) 
           :AliKalmanTrack() 
{
  //
  // Constructor from AliESDtrack
  //

  SetLabel(t.GetLabel());
  SetChi2(0.);
  SetMass(t.GetMass());
  SetNumberOfClusters(t.GetTRDclusters(fIndex)); 
  Int_t ncl = t.GetTRDclusters(fIndexBackup);
  for (UInt_t i=ncl;i<kMAXCLUSTERSPERTRACK;i++) {
    fIndexBackup[i]=0;
    fIndex[i] = 0; //MI store indexes
  }
  fdEdx=t.GetTRDsignal();  
  fDE =0;     
  for (Int_t i=0;i<kNplane;i++){
    for (Int_t j=0;j<kNslice;j++){
      fdEdxPlane[i][j] = t.GetTRDsignals(i,j);
    }
    fTimBinPlane[i] = t.GetTRDTimBin(i);
  }

  fLhElectron = 0.0;
  fNWrong = 0;
  fStopped = 0;
  fNRotate = 0;
  fNExpected =0;
  fNExpectedLast=0;
  fNdedx = 0;
  fNCross =0;
  fNLast  =0;
  fChi2Last =0;
  fBackupTrack =0;

  fAlpha = t.GetAlpha();
  if      (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
  else if (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();

  Double_t x, p[5]; t.GetExternalParameters(x,p);
  //Conversion of the covariance matrix
  Double_t c[15]; t.GetExternalCovariance(c);
  if (t.GetStatus()&AliESDtrack::kTRDbackup){
    t.GetOuterExternalParameters(fAlpha,x,p);
    t.GetOuterExternalCovariance(c);
    if      (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
    else if (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();
  }

  fX=x;

  fY=p[0];
  fZ=p[1]; SaveLocalConvConst();
  fT=p[3]; x=GetLocalConvConst();
  fC=p[4]/x;
  fE=fC*fX - p[2];   


  c[10]/=x; c[11]/=x; c[12]/=x; c[13]/=x; c[14]/=x*x;

  Double_t c22=fX*fX*c[14] - 2*fX*c[12] + c[5];
  Double_t c32=fX*c[13] - c[8];
  Double_t c20=fX*c[10] - c[3], c21=fX*c[11] - c[4], c42=fX*c[14] - c[12];

  fCyy=c[0 ];
  fCzy=c[1 ];   fCzz=c[2 ];
  fCey=c20;     fCez=c21;     fCee=c22;
  fCty=c[6 ];   fCtz=c[7 ];   fCte=c32;   fCtt=c[9 ];
  fCcy=c[10];   fCcz=c[11];   fCce=c42;   fCct=c[13]; fCcc=c[14];  

  // Initialization [SR, GSI, 18.02.2003]
  for(UInt_t i=0; i<kMAXCLUSTERSPERTRACK; i++) {
    fdQdl[i] = 0;
    //    fIndex[i] = 0; //MI store indexes
  }

  for (Int_t i=0;i<3;i++) { fBudget[i]=0;};
  if ((t.GetStatus()&AliESDtrack::kTIME) == 0) return;
  StartTimeIntegral();
  Double_t times[10]; t.GetIntegratedTimes(times); SetIntegratedTimes(times);
  SetIntegratedLength(t.GetIntegratedLength());

}  

//____________________________________________________________________________
AliTRDtrack::~AliTRDtrack()
{
  //
  // Destructor
  //

  if (fBackupTrack) delete fBackupTrack;
  fBackupTrack = 0;

}

//____________________________________________________________________________
AliTRDtrack &AliTRDtrack::operator=(const AliTRDtrack &t)
{
  //
  // Assignment operator
  //

  fLhElectron = 0.0;
  fNWrong = 0;
  fStopped = 0;
  fNRotate = 0;
  fNExpected =0;
  fNExpectedLast=0;
  fNdedx = 0;
  fNCross =0;
  fNLast  =0;
  fChi2Last =0;
  fBackupTrack =0;

  fAlpha = t.GetAlpha();
  if      (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
  else if (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();

  return *this;

}

//____________________________________________________________________________
Float_t AliTRDtrack::StatusForTOF()
{
  //
  // Defines the status of the TOF extrapolation
  //

  Float_t res = (0.2 + 0.8*(fN/(fNExpected+5.)))*(0.4+0.6*fTracklets[5].GetN()/20.);
  res *= (0.25+0.8*40./(40.+fBudget[2]));
  return res;

  Int_t status=0;
  if (GetNumberOfClusters()<20) return 0;   //
  if (fN>110&&fChi2/(Float_t(fN))<3) return 3;            //gold
  if (fNLast>30&&fChi2Last/(Float_t(fNLast))<3) return 3; //gold
  if (fNLast>20&&fChi2Last/(Float_t(fNLast))<2) return 3; //gold
  if (fNLast/(fNExpectedLast+3.)>0.8 && fChi2Last/Float_t(fNLast)<5&&fNLast>20) return 2; //silber
  if (fNLast>5 &&((fNLast+1.)/(fNExpectedLast+1.))>0.8&&fChi2Last/(fNLast-5.)<6)   return 1; 
  
  return status;

}
            
//_____________________________________________________________________________
void AliTRDtrack::GetExternalCovariance(Double_t cc[15]) const 
{
  //
  // This function returns external representation of the covriance matrix.
  //

  Double_t a=GetLocalConvConst();

  Double_t c22=fX*fX*fCcc-2*fX*fCce+fCee;
  Double_t c32=fX*fCct-fCte;
  Double_t c20=fX*fCcy-fCey, c21=fX*fCcz-fCez, c42=fX*fCcc-fCce;

  cc[0 ]=fCyy;
  cc[1 ]=fCzy;   cc[2 ]=fCzz;
  cc[3 ]=c20;    cc[4 ]=c21;    cc[5 ]=c22;
  cc[6 ]=fCty;   cc[7 ]=fCtz;   cc[8 ]=c32;   cc[9 ]=fCtt;
  cc[10]=fCcy*a; cc[11]=fCcz*a; cc[12]=c42*a; cc[13]=fCct*a; cc[14]=fCcc*a*a; 
  
}               
                       
//_____________________________________________________________________________
void AliTRDtrack::GetCovariance(Double_t cc[15]) const 
{
  //
  // Returns the track covariance matrix
  //

  cc[0]=fCyy;
  cc[1]=fCzy;  cc[2]=fCzz;
  cc[3]=fCey;  cc[4]=fCez;  cc[5]=fCee;
  cc[6]=fCcy;  cc[7]=fCcz;  cc[8]=fCce;  cc[9]=fCcc;
  cc[10]=fCty; cc[11]=fCtz; cc[12]=fCte; cc[13]=fCct; cc[14]=fCtt;
  
}    

//_____________________________________________________________________________
Int_t AliTRDtrack::Compare(const TObject *o) const 
{
  //
  // Compares tracks according to their Y2 or curvature
  //

  AliTRDtrack *t=(AliTRDtrack*)o;
  //  Double_t co=t->GetSigmaY2();
  //  Double_t c =GetSigmaY2();

  Double_t co=TMath::Abs(t->GetC());
  Double_t c =TMath::Abs(GetC());  

  if      (c>co) return 1;
  else if (c<co) return -1;
  return 0;

}                

//_____________________________________________________________________________
void AliTRDtrack::CookdEdx(Double_t low, Double_t up) {
  //-----------------------------------------------------------------
  // Calculates dE/dX within the "low" and "up" cuts.
  //-----------------------------------------------------------------

  Int_t i;
  //Int_t nc=GetNumberOfClusters(); 
  Int_t nc=fNdedx; 
  if (nc<10)  {
    SetdEdx(0);
    return;
  }

  Float_t sorted[kMAXCLUSTERSPERTRACK];
  for (i=0; i < nc; i++) {
    sorted[i]=fdQdl[i];
  }
  Int_t nl=Int_t(low*nc), nu=Int_t(up*nc);
  Float_t dedx=0;
  //for (i=nl; i<=nu; i++) dedx += sorted[i];
  //dedx /= (nu-nl+1);
  for (i=0; i<nc; i++) dedx += sorted[i];       // ADDED by PS
  if((nu-nl)) dedx /= (nu-nl);                  // ADDED by PS

  //SetdEdx(dedx);
  //
  // now real truncated mean
  for (i=0; i < nc; i++) {
    sorted[i]=TMath::Abs(fdQdl[i]);
  }
  Int_t * index = new Int_t[nc];
  TMath::Sort(nc, sorted, index,kFALSE);
  dedx=0;
  for (i=nl; i<=nu; i++) dedx += sorted[index[i]];
  dedx /= (nu-nl+1);
  fdEdxT = dedx;
  delete [] index;
  SetdEdx(dedx);

}                     

//_____________________________________________________________________________
Int_t AliTRDtrack::PropagateTo(Double_t xk,Double_t x0,Double_t rho)
{
  // Propagates a track of particle with mass=pm to a reference plane 
  // defined by x=xk through media of density=rho and radiationLength=x0

  if (xk == fX) return 1;

  if (TMath::Abs(fC*xk - fE) >= 0.90000) {
    //    Int_t n=GetNumberOfClusters();
    //if (n>4) cerr << n << " AliTRDtrack: Propagation failed, \tPt = " 
    //              << GetPt() << "\t" << GetLabel() << "\t" << GetMass() << endl;
    return 0;
  }
  Double_t lcc=GetLocalConvConst();

  // track Length measurement [SR, GSI, 17.02.2003]
  Double_t oldX = fX, oldY = fY, oldZ = fZ;  

  Double_t x1=fX, x2=x1+(xk-x1), dx=x2-x1, y1=fY, z1=fZ;
  Double_t c1=fC*x1 - fE;
  if((c1*c1) > 1) return 0;
  Double_t r1=sqrt(1.- c1*c1);
  Double_t c2=fC*x2 - fE; 
  if((c2*c2) > 1) return 0;
  Double_t r2=sqrt(1.- c2*c2);

  fY += dx*(c1+c2)/(r1+r2);
  fZ += dx*(c1+c2)/(c1*r2 + c2*r1)*fT;

  //f = F - 1
  Double_t rr=r1+r2, cc=c1+c2, xx=x1+x2;
  Double_t f02=-dx*(2*rr + cc*(c1/r1 + c2/r2))/(rr*rr);
  Double_t f04= dx*(rr*xx + cc*(c1*x1/r1+c2*x2/r2))/(rr*rr);
  Double_t cr=c1*r2+c2*r1;
  Double_t f12=-dx*fT*(2*cr + cc*(c2*c1/r1-r1 + c1*c2/r2-r2))/(cr*cr);
  Double_t f13= dx*cc/cr;
  Double_t f14=dx*fT*(cr*xx-cc*(r1*x2-c2*c1*x1/r1+r2*x1-c1*c2*x2/r2))/(cr*cr);

  //b = C*ft
  Double_t b00=f02*fCey + f04*fCcy, b01=f12*fCey + f14*fCcy + f13*fCty;
  Double_t b10=f02*fCez + f04*fCcz, b11=f12*fCez + f14*fCcz + f13*fCtz;
  Double_t b20=f02*fCee + f04*fCce, b21=f12*fCee + f14*fCce + f13*fCte;
  Double_t b30=f02*fCte + f04*fCct, b31=f12*fCte + f14*fCct + f13*fCtt;
  Double_t b40=f02*fCce + f04*fCcc, b41=f12*fCce + f14*fCcc + f13*fCct;

  //a = f*b = f*C*ft
  Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a11=f12*b21+f14*b41+f13*b31;

  //F*C*Ft = C + (a + b + bt)
  fCyy += a00 + 2*b00;
  fCzy += a01 + b01 + b10;
  fCey += b20;
  fCty += b30;
  fCcy += b40;
  fCzz += a11 + 2*b11;
  fCez += b21;
  fCtz += b31;
  fCcz += b41;

  fX=x2;                                                     

  //Change of the magnetic field *************
  SaveLocalConvConst();
  cc=fC;
  fC*=lcc/GetLocalConvConst();
  fE+=fX*(fC-cc);

  //Multiple scattering  ******************
  Double_t d=sqrt((x1-fX)*(x1-fX)+(y1-fY)*(y1-fY)+(z1-fZ)*(z1-fZ));
  Double_t p2=(1.+ GetTgl()*GetTgl())/(Get1Pt()*Get1Pt());
  Double_t beta2=p2/(p2 + GetMass()*GetMass());
  Double_t theta2=14.1*14.1/(beta2*p2*1e6)*d/x0*rho;

  Double_t ey=fC*fX - fE, ez=fT;
  Double_t xz=fC*ez, zz1=ez*ez+1, xy=fE+ey;
  
  fCee += (2*ey*ez*ez*fE+1-ey*ey+ez*ez+fE*fE*ez*ez)*theta2;
  fCte += ez*zz1*xy*theta2;
  fCtt += zz1*zz1*theta2;
  fCce += xz*ez*xy*theta2;
  fCct += xz*zz1*theta2;
  fCcc += xz*xz*theta2;
  /*
  Double_t dc22 = (1-ey*ey+xz*xz*fX*fX)*theta2;
  Double_t dc32 = (xz*fX*zz1)*theta2;
  Double_t dc33 = (zz1*zz1)*theta2;
  Double_t dc42 = (xz*fX*xz)*theta2;
  Double_t dc43 = (zz1*xz)*theta2;
  Double_t dc44 = (xz*xz)*theta2; 
  fCee += dc22;
  fCte += dc32;
  fCtt += dc33;
  fCce += dc42;
  fCct += dc43;
  fCcc += dc44;
  */
  //Energy losses************************
  if((5940*beta2/(1-beta2+1e-10) - beta2) < 0) return 0;

  Double_t dE=0.153e-3/beta2*(log(5940*beta2/(1-beta2+1e-10)) - beta2)*d*rho;
  Float_t budget = d* rho;
  fBudget[0] +=budget;
  //
  // suspicious part - think about it ?
  Double_t kinE =  TMath::Sqrt(p2);
  if (dE>0.8*kinE) dE = 0.8*kinE;  //      
  if (dE<0)        dE = 0.0;       // not valid region for Bethe bloch 
  //
  //
  fDE+=dE;
  if (x1 < x2) dE=-dE;
  cc=fC;
  fC*=(1.- sqrt(p2+GetMass()*GetMass())/p2*dE);
  fE+=fX*(fC-cc);    
  //  Double_t sigmade = 0.1*dE*TMath::Sqrt(TMath::Sqrt(1+fT*fT)*90./(d+0.0001));   // 20 percent fluctuation - normalized to some length 
  Double_t sigmade = 0.07*TMath::Sqrt(TMath::Abs(dE));   // energy loss fluctuation 
  Double_t sigmac2 = sigmade*sigmade*fC*fC*(p2+GetMass()*GetMass())/(p2*p2);
  fCcc += sigmac2;
  fCee += fX*fX*sigmac2;  

  // track time measurement [SR, GSI 17.02.2002]
  if (x1 < x2)
  if (IsStartedTimeIntegral()) {
    Double_t l2 = TMath::Sqrt((fX-oldX)*(fX-oldX) + (fY-oldY)*(fY-oldY) + (fZ-oldZ)*(fZ-oldZ));
    if (TMath::Abs(l2*fC)>0.0001){
      // make correction for curvature if neccesary
      l2 = 0.5*TMath::Sqrt((fX-oldX)*(fX-oldX) + (fY-oldY)*(fY-oldY));
      l2 = 2*TMath::ASin(l2*fC)/fC;
      l2 = TMath::Sqrt(l2*l2+(fZ-oldZ)*(fZ-oldZ));
    }
    AddTimeStep(l2);
  }

  return 1;            

}     

//_____________________________________________________________________________
Int_t AliTRDtrack::Update(const AliTRDcluster *c, Double_t chisq, UInt_t index
                        , Double_t h01)
{
  // Assignes found cluster to the track and updates track information

  Bool_t fNoTilt = kTRUE;
  if(TMath::Abs(h01) > 0.003) fNoTilt = kFALSE;
  // add angular effect to the error contribution -  MI
  Float_t tangent2 = (fC*fX-fE)*(fC*fX-fE);
  if (tangent2 < 0.90000){
    tangent2 = tangent2/(1.-tangent2);
  }
  Float_t errang = tangent2*0.04; //
  Float_t padlength = TMath::Sqrt(c->GetSigmaZ2()*12.);

  Double_t r00=c->GetSigmaY2() +errang, r01=0., r11=c->GetSigmaZ2()*100.;
  r00+=fCyy; r01+=fCzy; r11+=fCzz;
  Double_t det=r00*r11 - r01*r01;
  Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;

  Double_t k00=fCyy*r00+fCzy*r01, k01=fCyy*r01+fCzy*r11;
  Double_t k10=fCzy*r00+fCzz*r01, k11=fCzy*r01+fCzz*r11;
  Double_t k20=fCey*r00+fCez*r01, k21=fCey*r01+fCez*r11;
  Double_t k30=fCty*r00+fCtz*r01, k31=fCty*r01+fCtz*r11;
  Double_t k40=fCcy*r00+fCcz*r01, k41=fCcy*r01+fCcz*r11;

  Double_t dy=c->GetY() - fY, dz=c->GetZ() - fZ;
  Double_t cur=fC + k40*dy + k41*dz, eta=fE + k20*dy + k21*dz;


  if(fNoTilt) {
    if (TMath::Abs(cur*fX-eta) >= 0.90000) {
      //      Int_t n=GetNumberOfClusters();
      //if (n>4) cerr<<n<<" AliTRDtrack warning: Filtering failed !\n";
      return 0;
    }
    fY += k00*dy + k01*dz;
    fZ += k10*dy + k11*dz;
    fE  = eta;
    //fT += k30*dy + k31*dz;
    fC  = cur;
  }
  else {
    Double_t xuFactor = 100.;  // empirical factor set by C.Xu
                                // in the first tilt version      
    dy=c->GetY() - fY; dz=c->GetZ() - fZ;     
    dy=dy+h01*dz;
    Float_t add=0;
    if (TMath::Abs(dz)>padlength/2.){
      Float_t dy2 = c->GetY() - fY;
      Float_t sign = (dz>0) ? -1.: 1.;
      dy2+=h01*sign*padlength/2.;	
      dy  = dy2;
      add = 0;
    }
   


    r00=c->GetSigmaY2()+errang+add, r01=0., r11=c->GetSigmaZ2()*xuFactor; 
    r00+=(fCyy+2.0*h01*fCzy+h01*h01*fCzz);
    r01+=(fCzy+h01*fCzz);
    r11+=fCzz;

    det=r00*r11 - r01*r01;
    tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;

    k00=fCyy*r00+fCzy*(r01+h01*r00),k01=fCyy*r01+fCzy*(r11+h01*r01);
    k10=fCzy*r00+fCzz*(r01+h01*r00),k11=fCzy*r01+fCzz*(r11+h01*r01);
    k20=fCey*r00+fCez*(r01+h01*r00),k21=fCey*r01+fCez*(r11+h01*r01);
    k30=fCty*r00+fCtz*(r01+h01*r00),k31=fCty*r01+fCtz*(r11+h01*r01);
    k40=fCcy*r00+fCcz*(r01+h01*r00),k41=fCcy*r01+fCcz*(r11+h01*r01);  


    cur=fC + k40*dy + k41*dz; eta=fE + k20*dy + k21*dz;
    if (TMath::Abs(cur*fX-eta) >= 0.90000) {
      //      Int_t n=GetNumberOfClusters();
      //if (n>4) cerr<<n<<" AliTRDtrack warning: Filtering failed !\n";
      return 0;
    }                           
    fY += k00*dy + k01*dz;
    fZ += k10*dy + k11*dz;
    fE  = eta;
    fT += k30*dy + k31*dz;
    fC  = cur;
    
    k01+=h01*k00;
    k11+=h01*k10;
    k21+=h01*k20;
    k31+=h01*k30;
    k41+=h01*k40;  
    
  }
  Double_t c01=fCzy, c02=fCey, c03=fCty, c04=fCcy;
  Double_t c12=fCez, c13=fCtz, c14=fCcz;


  fCyy-=k00*fCyy+k01*fCzy; fCzy-=k00*c01+k01*fCzz;
  fCey-=k00*c02+k01*c12;   fCty-=k00*c03+k01*c13;
  fCcy-=k00*c04+k01*c14;
  
  fCzz-=k10*c01+k11*fCzz;
  fCez-=k10*c02+k11*c12;   fCtz-=k10*c03+k11*c13;
  fCcz-=k10*c04+k11*c14;
  
  fCee-=k20*c02+k21*c12;   fCte-=k20*c03+k21*c13;
  fCce-=k20*c04+k21*c14;
  
  fCtt-=k30*c03+k31*c13;
  fCct-=k40*c03+k41*c13;  
  //fCct-=k30*c04+k31*c14;  // symmetric formula MI  
  
  fCcc-=k40*c04+k41*c14;                 

  Int_t n=GetNumberOfClusters();
  fIndex[n]=index;
  SetNumberOfClusters(n+1);

  SetChi2(GetChi2()+chisq);
  //  cerr<<"in update: fIndex["<<fN<<"] = "<<index<<endl;

  return 1;     

}                     

//_____________________________________________________________________________
Int_t AliTRDtrack::UpdateMI(const AliTRDcluster *c, Double_t chisq, UInt_t index, Double_t h01, 
			    Int_t /*plane*/)
{
  // Assignes found cluster to the track and updates track information

  Bool_t fNoTilt = kTRUE;
  if(TMath::Abs(h01) > 0.003) fNoTilt = kFALSE;
  // add angular effect to the error contribution and make correction  -  MI
  //AliTRDclusterCorrection *corrector = AliTRDclusterCorrection::GetCorrection();
  // 
  Double_t tangent2 = (fC*fX-fE)*(fC*fX-fE);
  if (tangent2 < 0.90000){
    tangent2 = tangent2/(1.-tangent2);
  }
  Double_t tangent = TMath::Sqrt(tangent2);
  if ((fC*fX-fE)<0) tangent*=-1;
  //  Double_t correction = 0*plane;
  Double_t errang = tangent2*0.04;  //
  Double_t errsys =0.025*0.025*20;  //systematic error part 
  Float_t extend =1;
  if (c->GetNPads()==4) extend=2;
  //if (c->GetNPads()==5)  extend=3;
  //if (c->GetNPads()==6)  extend=3;
  //if (c->GetQ()<15) return 1;

  /*
  if (corrector!=0){
  //if (0){
    correction = corrector->GetCorrection(plane,c->GetLocalTimeBin(),tangent);
    if (TMath::Abs(correction)>0){
      //if we have info 
      errang     = corrector->GetSigma(plane,c->GetLocalTimeBin(),tangent);
      errang    *= errang;      
      errang    += tangent2*0.04;
    }
  }
  */
  //
  //  Double_t padlength = TMath::Sqrt(c->GetSigmaZ2()*12.);

  Double_t r00=(c->GetSigmaY2() +errang+errsys)*extend, r01=0., r11=c->GetSigmaZ2()*10000.;
  r00+=fCyy; r01+=fCzy; r11+=fCzz;
  Double_t det=r00*r11 - r01*r01;
  Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;

  Double_t k00=fCyy*r00+fCzy*r01, k01=fCyy*r01+fCzy*r11;
  Double_t k10=fCzy*r00+fCzz*r01, k11=fCzy*r01+fCzz*r11;
  Double_t k20=fCey*r00+fCez*r01, k21=fCey*r01+fCez*r11;
  Double_t k30=fCty*r00+fCtz*r01, k31=fCty*r01+fCtz*r11;
  Double_t k40=fCcy*r00+fCcz*r01, k41=fCcy*r01+fCcz*r11;

  Double_t dy=c->GetY() - fY, dz=c->GetZ() - fZ;
  Double_t cur=fC + k40*dy + k41*dz, eta=fE + k20*dy + k21*dz;


  if(fNoTilt) {
    if (TMath::Abs(cur*fX-eta) >= 0.90000) {
      //      Int_t n=GetNumberOfClusters();
      //if (n>4) cerr<<n<<" AliTRDtrack warning: Filtering failed !\n";
      return 0;
    }
    fY += k00*dy + k01*dz;
    fZ += k10*dy + k11*dz;
    fE  = eta;
    //fT += k30*dy + k31*dz;
    fC  = cur;
  }
  else {
    Double_t padlength = TMath::Sqrt(c->GetSigmaZ2()*12);
  
    Double_t xuFactor = 1000.;  // empirical factor set by C.Xu
                                // in the first tilt version      
    dy=c->GetY() - fY; dz=c->GetZ() - fZ;     
    //dy=dy+h01*dz+correction;
    
    Double_t tiltdz = dz;
    if (TMath::Abs(tiltdz)>padlength/2.) {
      tiltdz = TMath::Sign(padlength/2,dz);
    }
    //    dy=dy+h01*dz;
    dy=dy+h01*tiltdz;

    Double_t add=0;
    if (TMath::Abs(dz)>padlength/2.){
      //Double_t dy2 = c->GetY() - fY;
      //Double_t sign = (dz>0) ? -1.: 1.;
      //dy2-=h01*sign*padlength/2.;	
      //dy = dy2;
      add =1;
    }
    Double_t s00 = (c->GetSigmaY2()+errang)*extend+errsys+add;  // error pad
    Double_t s11 = c->GetSigmaZ2()*xuFactor;   // error pad-row
    //
    r00 = fCyy + 2*fCzy*h01 + fCzz*h01*h01+s00;
    r01 = fCzy + fCzz*h01;
    r11 = fCzz + s11;
    det = r00*r11 - r01*r01;
    // inverse matrix
    tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;

    // K matrix
    k00=fCyy*r00+fCzy*(r01+h01*r00),k01=fCyy*r01+fCzy*(r11+h01*r01);
    k10=fCzy*r00+fCzz*(r01+h01*r00),k11=fCzy*r01+fCzz*(r11+h01*r01);
    k20=fCey*r00+fCez*(r01+h01*r00),k21=fCey*r01+fCez*(r11+h01*r01);
    k30=fCty*r00+fCtz*(r01+h01*r00),k31=fCty*r01+fCtz*(r11+h01*r01);
    k40=fCcy*r00+fCcz*(r01+h01*r00),k41=fCcy*r01+fCcz*(r11+h01*r01);  
    //
    //Update measurement
    cur=fC + k40*dy + k41*dz; eta=fE + k20*dy + k21*dz;
    if (TMath::Abs(cur*fX-eta) >= 0.90000) {
      //Int_t n=GetNumberOfClusters();
      //      if (n>4) cerr<<n<<" AliTRDtrack warning: Filtering failed !\n";
      return 0;
    }                           
    fY += k00*dy + k01*dz;
    fZ += k10*dy + k11*dz;
    fE  = eta;
    fT += k30*dy + k31*dz;
    fC  = cur;
    
    k01+=h01*k00;
    k11+=h01*k10;
    k21+=h01*k20;
    k31+=h01*k30;
    k41+=h01*k40;  
    
  }
  //Update covariance
  //
  //
  Double_t oldyy = fCyy, oldzz = fCzz; //, oldee=fCee, oldcc =fCcc;
  Double_t oldzy = fCzy, oldey = fCey, oldty=fCty, oldcy =fCcy;
  Double_t oldez = fCez, oldtz = fCtz, oldcz=fCcz;
  //Double_t oldte = fCte, oldce = fCce;
  //Double_t oldct = fCct;

  fCyy-=k00*oldyy+k01*oldzy;   
  fCzy-=k10*oldyy+k11*oldzy;
  fCey-=k20*oldyy+k21*oldzy;   
  fCty-=k30*oldyy+k31*oldzy;
  fCcy-=k40*oldyy+k41*oldzy;  
  //
  fCzz-=k10*oldzy+k11*oldzz;
  fCez-=k20*oldzy+k21*oldzz;   
  fCtz-=k30*oldzy+k31*oldzz;
  fCcz-=k40*oldzy+k41*oldzz;
  //
  fCee-=k20*oldey+k21*oldez;   
  fCte-=k30*oldey+k31*oldez;
  fCce-=k40*oldey+k41*oldez;
  //
  fCtt-=k30*oldty+k31*oldtz;
  fCct-=k40*oldty+k41*oldtz;
  //
  fCcc-=k40*oldcy+k41*oldcz;                 
  //

  Int_t n=GetNumberOfClusters();
  fIndex[n]=index;
  SetNumberOfClusters(n+1);

  SetChi2(GetChi2()+chisq);
  //  cerr<<"in update: fIndex["<<fN<<"] = "<<index<<endl;

  return 1;      

}                     

//_____________________________________________________________________________
Int_t AliTRDtrack::UpdateMI(const AliTRDtracklet &tracklet)
{
  //
  // Assignes found tracklet to the track and updates track information
  //
  //
  Double_t r00=(tracklet.GetTrackletSigma2()), r01=0., r11= 10000.;
  r00+=fCyy; r01+=fCzy; r11+=fCzz;
  //
  Double_t det=r00*r11 - r01*r01;
  Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
  //

  Double_t dy=tracklet.GetY() - fY, dz=tracklet.GetZ() - fZ;

  
  Double_t s00 = tracklet.GetTrackletSigma2();  // error pad
  Double_t s11 = 100000;   // error pad-row
  Float_t  h01 = tracklet.GetTilt();
  //
  //  r00 = fCyy + 2*fCzy*h01 + fCzz*h01*h01+s00;
  r00 = fCyy + fCzz*h01*h01+s00;
  //  r01 = fCzy + fCzz*h01;
  r01 = fCzy ;
  r11 = fCzz + s11;
  det = r00*r11 - r01*r01;
  // inverse matrix
  tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;

  Double_t k00=fCyy*r00+fCzy*r01, k01=fCyy*r01+fCzy*r11;
  Double_t k10=fCzy*r00+fCzz*r01, k11=fCzy*r01+fCzz*r11;
  Double_t k20=fCey*r00+fCez*r01, k21=fCey*r01+fCez*r11;
  Double_t k30=fCty*r00+fCtz*r01, k31=fCty*r01+fCtz*r11;
  Double_t k40=fCcy*r00+fCcz*r01, k41=fCcy*r01+fCcz*r11;
  
  // K matrix
//   k00=fCyy*r00+fCzy*(r01+h01*r00),k01=fCyy*r01+fCzy*(r11+h01*r01);
//   k10=fCzy*r00+fCzz*(r01+h01*r00),k11=fCzy*r01+fCzz*(r11+h01*r01);
//   k20=fCey*r00+fCez*(r01+h01*r00),k21=fCey*r01+fCez*(r11+h01*r01);
//   k30=fCty*r00+fCtz*(r01+h01*r00),k31=fCty*r01+fCtz*(r11+h01*r01);
//   k40=fCcy*r00+fCcz*(r01+h01*r00),k41=fCcy*r01+fCcz*(r11+h01*r01);  
  //
  //Update measurement
  Double_t cur=fC + k40*dy + k41*dz, eta=fE + k20*dy + k21*dz;  
  //  cur=fC + k40*dy + k41*dz; eta=fE + k20*dy + k21*dz;
  if (TMath::Abs(cur*fX-eta) >= 0.90000) {
    //Int_t n=GetNumberOfClusters();
    //      if (n>4) cerr<<n<<" AliTRDtrack warning: Filtering failed !\n";
    return 0;
  }                           
//   k01+=h01*k00;
//   k11+=h01*k10;
//   k21+=h01*k20;
//   k31+=h01*k30;
//   k41+=h01*k40;  


  fY += k00*dy + k01*dz;
  fZ += k10*dy + k11*dz;
  fE  = eta;
  fT += k30*dy + k31*dz;
  fC  = cur;
    
  
  //Update covariance
  //
  //
  Double_t oldyy = fCyy, oldzz = fCzz; //, oldee=fCee, oldcc =fCcc;
  Double_t oldzy = fCzy, oldey = fCey, oldty=fCty, oldcy =fCcy;
  Double_t oldez = fCez, oldtz = fCtz, oldcz=fCcz;
  //Double_t oldte = fCte, oldce = fCce;
  //Double_t oldct = fCct;

  fCyy-=k00*oldyy+k01*oldzy;   
  fCzy-=k10*oldyy+k11*oldzy;
  fCey-=k20*oldyy+k21*oldzy;   
  fCty-=k30*oldyy+k31*oldzy;
  fCcy-=k40*oldyy+k41*oldzy;  
  //
  fCzz-=k10*oldzy+k11*oldzz;
  fCez-=k20*oldzy+k21*oldzz;   
  fCtz-=k30*oldzy+k31*oldzz;
  fCcz-=k40*oldzy+k41*oldzz;
  //
  fCee-=k20*oldey+k21*oldez;   
  fCte-=k30*oldey+k31*oldez;
  fCce-=k40*oldey+k41*oldez;
  //
  fCtt-=k30*oldty+k31*oldtz;
  fCct-=k40*oldty+k41*oldtz;
  //
  fCcc-=k40*oldcy+k41*oldcz;                 
  //
  /*
  Int_t n=GetNumberOfClusters();
  fIndex[n]=index;
  SetNumberOfClusters(n+1);

  SetChi2(GetChi2()+chisq);
  //  cerr<<"in update: fIndex["<<fN<<"] = "<<index<<endl;
  */

  return 1;      

}                     

//_____________________________________________________________________________
Int_t AliTRDtrack::Rotate(Double_t alpha, Bool_t absolute)
{
  // Rotates track parameters in R*phi plane
  // if absolute rotation alpha is in global system
  // otherwise alpha rotation is relative to the current rotation angle
  
  if (absolute) {
    alpha -= fAlpha;
  }
  else{
    fNRotate++;
  }

  fAlpha += alpha;
  if (fAlpha<-TMath::Pi()) fAlpha += 2*TMath::Pi();
  if (fAlpha>=TMath::Pi()) fAlpha -= 2*TMath::Pi();

  Double_t x1=fX, y1=fY;
  Double_t ca=cos(alpha), sa=sin(alpha);
  Double_t r1=fC*fX - fE;

  fX = x1*ca + y1*sa;
  fY =-x1*sa + y1*ca;
  if((r1*r1) > 1) return 0;
  fE=fE*ca + (fC*y1 + sqrt(1.- r1*r1))*sa;

  Double_t r2=fC*fX - fE;
  if (TMath::Abs(r2) >= 0.90000) {
    Int_t n=GetNumberOfClusters();
    if (n>4) cerr<<n<<" AliTRDtrack warning: Rotation failed !\n";
    return 0;
  }

  if((r2*r2) > 1) return 0;
  Double_t y0=fY + sqrt(1.- r2*r2)/fC;
  if ((fY-y0)*fC >= 0.) {
    Int_t n=GetNumberOfClusters();
    if (n>4) cerr<<n<<" AliTRDtrack warning: Rotation failed !!!\n";
    return 0;
  }

  //f = F - 1
  Double_t f00=ca-1,    f24=(y1 - r1*x1/sqrt(1.- r1*r1))*sa,
           f20=fC*sa,  f22=(ca + sa*r1/sqrt(1.- r1*r1))-1;

  //b = C*ft
  Double_t b00=fCyy*f00, b02=fCyy*f20+fCcy*f24+fCey*f22;
  Double_t b10=fCzy*f00, b12=fCzy*f20+fCcz*f24+fCez*f22;
  Double_t b20=fCey*f00, b22=fCey*f20+fCce*f24+fCee*f22;
  Double_t b30=fCty*f00, b32=fCty*f20+fCct*f24+fCte*f22;
  Double_t b40=fCcy*f00, b42=fCcy*f20+fCcc*f24+fCce*f22;

  //a = f*b = f*C*ft
  Double_t a00=f00*b00, a02=f00*b02, a22=f20*b02+f24*b42+f22*b22;

  //F*C*Ft = C + (a + b + bt)
  fCyy += a00 + 2*b00;
  fCzy += b10;
  fCey += a02+b20+b02;
  fCty += b30;
  fCcy += b40;
  fCez += b12;
  fCte += b32;
  fCee += a22 + 2*b22;
  fCce += b42;

  return 1;                            

}                         

//_____________________________________________________________________________
Double_t AliTRDtrack::GetPredictedChi2(const AliTRDcluster *c, Double_t h01) const
{
  //
  // Returns the track chi2
  //  

  Bool_t fNoTilt = kTRUE;
  if(TMath::Abs(h01) > 0.003) fNoTilt = kFALSE;
  Double_t chi2, dy, r00, r01, r11;

  if(fNoTilt) {
    dy=c->GetY() - fY;
    r00=c->GetSigmaY2();    
    chi2 = (dy*dy)/r00;    
  }
  else {
    Double_t padlength = TMath::Sqrt(c->GetSigmaZ2()*12);
    //
    r00=c->GetSigmaY2(); r01=0.; r11=c->GetSigmaZ2();
    r00+=fCyy; r01+=fCzy; r11+=fCzz;

    Double_t det=r00*r11 - r01*r01;
    if (TMath::Abs(det) < 1.e-10) {
      Int_t n=GetNumberOfClusters(); 
      if (n>4) cerr<<n<<" AliTRDtrack warning: Singular matrix !\n";
      return 1e10;
    }
    Double_t tmp=r00; r00=r11; r11=tmp; r01=-r01;
    Double_t dy=c->GetY() - fY, dz=c->GetZ() - fZ;
    Double_t tiltdz = dz;
    if (TMath::Abs(tiltdz)>padlength/2.) {
      tiltdz = TMath::Sign(padlength/2,dz);
    }
    //    dy=dy+h01*dz;
    dy=dy+h01*tiltdz;

    chi2 = (dy*r00*dy + 2*r01*dy*dz + dz*r11*dz)/det; 
  }

  return chi2;

}      

//_________________________________________________________________________
void AliTRDtrack::GetPxPyPz(Double_t& px, Double_t& py, Double_t& pz) const
{
  // Returns reconstructed track momentum in the global system.

  Double_t pt=TMath::Abs(GetPt()); // GeV/c
  Double_t r=fC*fX-fE;

  Double_t y0; 
  if(r > 1) { py = pt; px = 0; }
  else if(r < -1) { py = -pt; px = 0; }
  else {
    y0=fY + sqrt(1.- r*r)/fC;  
    px=-pt*(fY-y0)*fC;    //cos(phi);
    py=-pt*(fE-fX*fC);   //sin(phi);
  }
  pz=pt*fT;
  Double_t tmp=px*TMath::Cos(fAlpha) - py*TMath::Sin(fAlpha);
  py=px*TMath::Sin(fAlpha) + py*TMath::Cos(fAlpha);
  px=tmp;            

}                                

//_________________________________________________________________________
void AliTRDtrack::GetGlobalXYZ(Double_t& x, Double_t& y, Double_t& z) const
{
  // Returns reconstructed track coordinates in the global system.

  x = fX; y = fY; z = fZ; 
  Double_t tmp=x*TMath::Cos(fAlpha) - y*TMath::Sin(fAlpha);
  y=x*TMath::Sin(fAlpha) + y*TMath::Cos(fAlpha);
  x=tmp;            

}                                

//_________________________________________________________________________
void AliTRDtrack::ResetCovariance() 
{
  //
  // Resets covariance matrix
  //

  fCyy*=10.;
  fCzy=0.;  fCzz*=10.;
  fCey=0.;  fCez=0.;  fCee*=10.;
  fCty=0.;  fCtz=0.;  fCte=0.;  fCtt*=10.;
  fCcy=0.;  fCcz=0.;  fCce=0.;  fCct=0.;  fCcc*=10.;  

}                                                         

//_____________________________________________________________________________
void AliTRDtrack::ResetCovariance(Float_t mult) 
{
  //
  // Resets covariance matrix
  //

  fCyy*=mult;
  fCzy*=0.;  fCzz*=1.;
  fCey*=0.;  fCez*=0.;  fCee*=mult;
  fCty*=0.;  fCtz*=0.;  fCte*=0.;  fCtt*=1.;
  fCcy*=0.;  fCcz*=0.;  fCce*=0.;  fCct*=0.;  fCcc*=mult;  

}                                                         

//_____________________________________________________________________________
void AliTRDtrack::MakeBackupTrack()
{
  //
  // Creates a backup track
  //

  if (fBackupTrack) delete fBackupTrack;
  fBackupTrack = new AliTRDtrack(*this);
  
}

//_____________________________________________________________________________
Int_t AliTRDtrack::GetProlongation(Double_t xk, Double_t &y, Double_t &z)
{
  //
  // Find prolongation at given x
  // return 0 if not exist
  
  Double_t c1=fC*fX - fE;
  if (TMath::Abs(c1)>1.) return 0;
  Double_t r1=TMath::Sqrt(1.- c1*c1);
  Double_t c2=fC*xk - fE;
  if (TMath::Abs(c2)>1.) return 0;  
  Double_t r2=TMath::Sqrt(1.- c2*c2);
  y =fY + (xk-fX)*(c1+c2)/(r1+r2);
  z =fZ + (xk-fX)*(c1+c2)/(c1*r2 + c2*r1)*fT;

  return 1;
  
}

//_____________________________________________________________________________
Int_t   AliTRDtrack::PropagateToX(Double_t xr, Double_t step)
{
  //
  // Propagate track to given x  position 
  // works inside of the 20 degree segmentation (local cooordinate frame for TRD , TPC, TOF)
  // 
  // material budget from geo manager
  // 
  Double_t  xyz0[3], xyz1[3],y,z;
  const Double_t kAlphac  = TMath::Pi()/9.;   
  const Double_t kTalphac = TMath::Tan(kAlphac*0.5);
  // critical alpha  - cross sector indication
  //
  Double_t dir = (fX>xr) ? -1.:1.;
  // direction +-
  for (Double_t x=fX+dir*step;dir*x<dir*xr;x+=dir*step){
    //
    GetGlobalXYZ(xyz0[0],xyz0[1],xyz0[2]);	
    GetProlongation(x,y,z);
    xyz1[0] = x*TMath::Cos(fAlpha)+y*TMath::Sin(fAlpha); 
    xyz1[1] = x*TMath::Sin(fAlpha)-y*TMath::Cos(fAlpha);
    xyz1[2] = z;
    Double_t param[7];
    AliKalmanTrack::MeanMaterialBudget(xyz0,xyz1,param);
    //
    if (param[0]>0&&param[1]>0) PropagateTo(x,param[1],param[0]);
    if (fY>fX*kTalphac){
      Rotate(-kAlphac);
    }
    if (fY<-fX*kTalphac){
      Rotate(kAlphac);
    }
  }
  //
  PropagateTo(xr);

  return 0;

}

//_____________________________________________________________________________
Int_t   AliTRDtrack::PropagateToR(Double_t r,Double_t step)
{
  //
  // propagate track to the radial position
  // rotation always connected to the last track position
  //
  Double_t  xyz0[3], xyz1[3],y,z; 
  Double_t radius = TMath::Sqrt(fX*fX+fY*fY);
  Double_t dir = (radius>r) ? -1.:1.;   // direction +-
  //
  for (Double_t x=radius+dir*step;dir*x<dir*r;x+=dir*step){
    GetGlobalXYZ(xyz0[0],xyz0[1],xyz0[2]);	
    Double_t alpha = TMath::ATan2(xyz0[1],xyz0[0]);
    Rotate(alpha,kTRUE);
    GetGlobalXYZ(xyz0[0],xyz0[1],xyz0[2]);	
    GetProlongation(x,y,z);
    xyz1[0] = x*TMath::Cos(alpha)+y*TMath::Sin(alpha); 
    xyz1[1] = x*TMath::Sin(alpha)-y*TMath::Cos(alpha);
    xyz1[2] = z;
    Double_t param[7];
    AliKalmanTrack::MeanMaterialBudget(xyz0,xyz1,param);
    if (param[1]<=0) param[1] =100000000;
    PropagateTo(x,param[1],param[0]);
  } 
  GetGlobalXYZ(xyz0[0],xyz0[1],xyz0[2]);	
  Double_t alpha = TMath::ATan2(xyz0[1],xyz0[0]);
  Rotate(alpha,kTRUE);
  GetGlobalXYZ(xyz0[0],xyz0[1],xyz0[2]);	
  GetProlongation(r,y,z);
  xyz1[0] = r*TMath::Cos(alpha)+y*TMath::Sin(alpha); 
  xyz1[1] = r*TMath::Sin(alpha)-y*TMath::Cos(alpha);
  xyz1[2] = z;
  Double_t param[7];
  AliKalmanTrack::MeanMaterialBudget(xyz0,xyz1,param);
  //
  if (param[1]<=0) param[1] =100000000;
  PropagateTo(r,param[1],param[0]);

  return 0;

}

//_____________________________________________________________________________
Int_t AliTRDtrack::GetSector() const
{
  //
  // Return the current sector
  //

  return Int_t(TVector2::Phi_0_2pi(fAlpha)
             / AliTRDgeometry::GetAlpha())
             % AliTRDgeometry::kNsect;

}

//_____________________________________________________________________________
Double_t  AliTRDtrack::Get1Pt() const                       
{ 
  //--------------------------------------------------------------
  // Returns the inverse Pt (1/GeV/c)
  // (or 1/"most probable pt", if the field is too weak)
  //--------------------------------------------------------------
  if (TMath::Abs(GetLocalConvConst()) > kVeryBigConvConst)
      return 1./kMostProbableMomentum/TMath::Sqrt(1.+ GetTgl()*GetTgl());
  return (TMath::Sign(1e-9,fC) + fC)*GetLocalConvConst();
}

//_____________________________________________________________________________
Double_t  AliTRDtrack::GetP() const                         
{ 
  //
  // Returns the total momentum
  //

  return TMath::Abs(GetPt())*sqrt(1.+GetTgl()*GetTgl());  

}

//_____________________________________________________________________________
Double_t AliTRDtrack::GetYat(Double_t xk) const            
{     
  //
  // This function calculates the Y-coordinate of a track at 
  // the plane x = xk.
  // Needed for matching with the TOF (I.Belikov)
  //

  Double_t c1 = fC*fX - fE;
  Double_t r1 = TMath::Sqrt(1.0 - c1*c1);
  Double_t c2 = fC*xk - fE;
  Double_t r2 = TMath::Sqrt(1.0-  c2*c2);
  return fY + (xk-fX)*(c1+c2)/(r1+r2);

}

//_____________________________________________________________________________
void AliTRDtrack::SetSampledEdx(Float_t q, Int_t i)    
{
  //
  // The sampled energy loss
  //

  Double_t s = GetSnp();
  Double_t t = GetTgl();
  q *= TMath::Sqrt((1-s*s)/(1+t*t));
  fdQdl[i] = q;

}     

 //_____________________________________________________________________________
void AliTRDtrack::SetSampledEdx(Float_t q) 
{
  //
  // The sampled energy loss
  //

  Double_t s = GetSnp();
  Double_t t = GetTgl();
  q*= TMath::Sqrt((1-s*s)/(1+t*t));
  fdQdl[fNdedx] = q;
  fNdedx++;

}     

//_____________________________________________________________________________
void AliTRDtrack::GetXYZ(Float_t r[3]) const 
{

  //---------------------------------------------------------------------
  // Returns the position of the track in the global coord. system 
  //---------------------------------------------------------------------

  Double_t cs = TMath::Cos(fAlpha);
  Double_t sn = TMath::Sin(fAlpha);
  r[0] = fX*cs - fY*sn; 
  r[1] = fX*sn + fY*cs; 
  r[2] = fZ;

}