* Possibility to reconstruct cosmic muon tracks that cross the ITS

[u/mrichter/AliRoot.git] / ITS / AliITStrackV2.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.              *
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 * 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.                  *
 **************************************************************************/

///////////////////////////////////////////////////////////////////////////
//                Implementation of the ITS track class
//
//          Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch
//     dEdx analysis by: Boris Batyunya, JINR, Boris.Batiounia@cern.ch
///////////////////////////////////////////////////////////////////////////
#include <TMath.h>

#include "AliCluster.h"
#include "AliTracker.h"
#include "AliESDtrack.h"
#include "AliITStrackV2.h"

const Int_t AliITStrackV2::fgkWARN = 5;

ClassImp(AliITStrackV2)


//____________________________________________________________________________
AliITStrackV2::AliITStrackV2() : AliKalmanTrack(),
  fdEdx(0),
  fESDtrack(0)
{
    for(Int_t i=0; i<2*kMaxLayer; i++) fIndex[i]=-1;
    for(Int_t i=0; i<4; i++) fdEdxSample[i]=0;
}


//____________________________________________________________________________
AliITStrackV2::AliITStrackV2(AliESDtrack& t,Bool_t c) throw (const Char_t *) :
  AliKalmanTrack(),
  fdEdx(t.GetITSsignal()),
  fESDtrack(&t)
{
  //------------------------------------------------------------------
  // Conversion ESD track -> ITS track.
  // If c==kTRUE, create the ITS track out of the constrained params.
  //------------------------------------------------------------------
  const AliExternalTrackParam *par=&t;
  if (c) {
    par=t.GetConstrainedParam();
    if (!par) throw "AliITStrackV2: conversion failed !\n";
  }
  Set(par->GetX(),par->GetAlpha(),par->GetParameter(),par->GetCovariance());

  //if (!Invariant()) throw "AliITStrackV2: conversion failed !\n";

  SetLabel(t.GetLabel());
  SetMass(t.GetMass());
  SetNumberOfClusters(t.GetITSclusters(fIndex));

  if (t.GetStatus()&AliESDtrack::kTIME) {
    StartTimeIntegral();
    Double_t times[10]; t.GetIntegratedTimes(times); SetIntegratedTimes(times);
    SetIntegratedLength(t.GetIntegratedLength());
  }

  for(Int_t i=0; i<4; i++) fdEdxSample[i]=0;
}

void AliITStrackV2::UpdateESDtrack(ULong_t flags) const {
  fESDtrack->UpdateTrackParams(this,flags);
}

//____________________________________________________________________________
AliITStrackV2::AliITStrackV2(const AliITStrackV2& t) : 
  AliKalmanTrack(t),
  fdEdx(t.fdEdx),
  fESDtrack(t.fESDtrack) 
{
  //------------------------------------------------------------------
  //Copy constructor
  //------------------------------------------------------------------
  Int_t i;
  for (i=0; i<4; i++) fdEdxSample[i]=t.fdEdxSample[i];
  for (i=0; i<2*kMaxLayer; i++) fIndex[i]=t.fIndex[i];
}

//_____________________________________________________________________________
Int_t AliITStrackV2::Compare(const TObject *o) const {
  //-----------------------------------------------------------------
  // This function compares tracks according to the their curvature
  //-----------------------------------------------------------------
  AliITStrackV2 *t=(AliITStrackV2*)o;
  //Double_t co=TMath::Abs(t->Get1Pt());
  //Double_t c =TMath::Abs(Get1Pt());
  Double_t co=t->GetSigmaY2()*t->GetSigmaZ2();
  Double_t c =GetSigmaY2()*GetSigmaZ2();
  if (c>co) return 1;
  else if (c<co) return -1;
  return 0;
}

//____________________________________________________________________________
Bool_t 
AliITStrackV2::PropagateToVertex(const AliESDVertex *v,Double_t d,Double_t x0) 
{
  //------------------------------------------------------------------
  //This function propagates a track to the minimal distance from the origin
  //------------------------------------------------------------------  
  Double_t bz=GetBz();
  if (PropagateToDCA(v,bz,kVeryBig))
   if (AliExternalTrackParam::CorrectForMaterial(d,x0,GetMass())) return kTRUE;
  return kFALSE;
}

//____________________________________________________________________________
Bool_t AliITStrackV2::
GetGlobalXYZat(Double_t xk, Double_t &x, Double_t &y, Double_t &z) const {
  //------------------------------------------------------------------
  //This function returns a track position in the global system
  //------------------------------------------------------------------
  Double_t r[3];
  Bool_t rc=GetXYZAt(xk, AliTracker::GetBz(), r);
  x=r[0]; y=r[1]; z=r[2]; 
  return rc;
}

//_____________________________________________________________________________
Double_t AliITStrackV2::GetPredictedChi2(const AliCluster *c) const {
  //-----------------------------------------------------------------
  // This function calculates a predicted chi2 increment.
  //-----------------------------------------------------------------
  Double_t p[2]={c->GetY(), c->GetZ()};
  Double_t cov[3]={c->GetSigmaY2(), 0., c->GetSigmaZ2()};
  return AliExternalTrackParam::GetPredictedChi2(p,cov);
}

//____________________________________________________________________________
Bool_t AliITStrackV2::PropagateTo(Double_t xk, Double_t d, Double_t x0) {
  //------------------------------------------------------------------
  //This function propagates a track
  //------------------------------------------------------------------
  Double_t oldX=GetX(), oldY=GetY(), oldZ=GetZ();
  
  Double_t bz=GetBz();
  if (!AliExternalTrackParam::PropagateTo(xk,bz)) return kFALSE;
 if (!AliExternalTrackParam::CorrectForMaterial(d,x0,GetMass())) return kFALSE;

  Double_t x=GetX(), y=GetY(), z=GetZ();
  if (IsStartedTimeIntegral() && x>oldX) {
    Double_t l2 = (x-oldX)*(x-oldX) + (y-oldY)*(y-oldY) + (z-oldZ)*(z-oldZ);
    AddTimeStep(TMath::Sqrt(l2));
  }

  return kTRUE;
}

//____________________________________________________________________________
Bool_t AliITStrackV2::Update(const AliCluster* c, Double_t chi2, Int_t index) 
{
  //------------------------------------------------------------------
  //This function updates track parameters
  //------------------------------------------------------------------
  Double_t p[2]={c->GetY(), c->GetZ()};
  Double_t cov[3]={c->GetSigmaY2(), 0., c->GetSigmaZ2()};

  if (!AliExternalTrackParam::Update(p,cov)) return kFALSE;

  if (!Invariant()) {
     AliWarning("Wrong invariant !");
     return kFALSE;
  }

  if (chi2<0) return kTRUE;

  Int_t n=GetNumberOfClusters();
  fIndex[n]=index;
  SetNumberOfClusters(n+1);
  SetChi2(GetChi2()+chi2);

  return kTRUE;
}

Bool_t AliITStrackV2::Invariant() const {
  //------------------------------------------------------------------
  // This function is for debugging purpose only
  //------------------------------------------------------------------
  Int_t n=GetNumberOfClusters();

  Double_t sP2=GetParameter()[2];
  if (TMath::Abs(sP2) >= kAlmost1){
     if (n>fgkWARN) Warning("Invariant","fP2=%f\n",sP2);
     return kFALSE;
  }
  Double_t sC00=GetCovariance()[0];
  if (sC00<=0 || sC00>9.) {
     if (n>fgkWARN) Warning("Invariant","fC00=%f\n",sC00); 
     return kFALSE;
  }
  Double_t sC11=GetCovariance()[2];
  if (sC11<=0 || sC11>9.) {
     if (n>fgkWARN) Warning("Invariant","fC11=%f\n",sC11); 
     return kFALSE;
  }
  Double_t sC22=GetCovariance()[5];
  if (sC22<=0 || sC22>1.) {
     if (n>fgkWARN) Warning("Invariant","fC22=%f\n",sC22); 
     return kFALSE;
  }
  Double_t sC33=GetCovariance()[9];
  if (sC33<=0 || sC33>1.) {
     if (n>fgkWARN) Warning("Invariant","fC33=%f\n",sC33); 
     return kFALSE;
  }
  Double_t sC44=GetCovariance()[14];
  if (sC44<=0 /*|| sC44>6e-5*/) {
     if (n>fgkWARN) Warning("Invariant","fC44=%f\n",sC44);
     return kFALSE;
  }

  return kTRUE;
}

//____________________________________________________________________________
Bool_t AliITStrackV2::Propagate(Double_t alp,Double_t xk) {
  //------------------------------------------------------------------
  //This function propagates a track
  //------------------------------------------------------------------
  Double_t bz=GetBz();
  if (!AliExternalTrackParam::Propagate(alp,xk,bz)) return kFALSE;

  if (!Invariant()) {
     AliWarning("Wrong invariant !");
     return kFALSE;
  }

  return kTRUE;
}

Bool_t AliITStrackV2::Improve(Double_t x0,Double_t xyz[3],Double_t ers[3]) {
  //------------------------------------------------------------------
  //This function improves angular track parameters
  //------------------------------------------------------------------
  Double_t cs=TMath::Cos(GetAlpha()), sn=TMath::Sin(GetAlpha());
//Double_t xv = xyz[0]*cs + xyz[1]*sn; // vertex
  Double_t yv =-xyz[0]*sn + xyz[1]*cs; // in the
  Double_t zv = xyz[2];                // local frame

  Double_t dy = Par(0) - yv, dz = Par(1) - zv;
  Double_t r2=GetX()*GetX() + dy*dy;
  Double_t p2=(1.+ GetTgl()*GetTgl())/(Get1Pt()*Get1Pt());
  Double_t beta2=p2/(p2 + GetMass()*GetMass());
  x0*=TMath::Sqrt((1.+ GetTgl()*GetTgl())/(1.- GetSnp()*GetSnp()));
  Double_t theta2=14.1*14.1/(beta2*p2*1e6)*x0;
  //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*x0*9.36*2.33;

  Double_t cnv=GetBz()*kB2C;
  {
    Double_t dummy = 4/r2 - GetC()*GetC();
    if (dummy < 0) return kFALSE;
    Double_t parp = 0.5*(GetC()*GetX() + dy*TMath::Sqrt(dummy));
    Double_t sigma2p = theta2*(1.- GetSnp()*GetSnp())*(1. + GetTgl()*GetTgl());
    sigma2p += Cov(0)/r2*(1.- dy*dy/r2)*(1.- dy*dy/r2);
    sigma2p += ers[1]*ers[1]/r2;
    sigma2p += 0.25*Cov(14)*cnv*cnv*GetX()*GetX();
    Double_t eps2p=sigma2p/(Cov(5) + sigma2p);
    Par(0) += Cov(3)/(Cov(5) + sigma2p)*(parp - GetSnp());
    Par(2)  = eps2p*GetSnp() + (1 - eps2p)*parp;
    Cov(5) *= eps2p;
    Cov(3) *= eps2p;
  }
  {
    Double_t parl=0.5*GetC()*dz/TMath::ASin(0.5*GetC()*TMath::Sqrt(r2));
    Double_t sigma2l=theta2;
    sigma2l += Cov(2)/r2 + Cov(0)*dy*dy*dz*dz/(r2*r2*r2);
    sigma2l += ers[2]*ers[2]/r2;
    Double_t eps2l = sigma2l/(Cov(9) + sigma2l);
    Par(1) += Cov(7 )/(Cov(9) + sigma2l)*(parl - Par(3));
    Par(4) += Cov(13)/(Cov(9) + sigma2l)*(parl - Par(3));
    Par(3)  = eps2l*Par(3) + (1-eps2l)*parl;
    Cov(9) *= eps2l; 
    Cov(13)*= eps2l; 
    Cov(7) *= eps2l; 
  }
  if (!Invariant()) return kFALSE;

  return kTRUE;
}

void AliITStrackV2::CookdEdx(Double_t low, Double_t up) {
  //-----------------------------------------------------------------
  // This function calculates dE/dX within the "low" and "up" cuts.
  // Origin: Boris Batyunya, JINR, Boris.Batiounia@cern.ch 
  //-----------------------------------------------------------------
  // The clusters order is: SSD-2, SSD-1, SDD-2, SDD-1, SPD-2, SPD-1

  Int_t i;
  Int_t nc=0;
  for (i=0; i<GetNumberOfClusters(); i++) {
    Int_t idx=GetClusterIndex(i);
    idx=(idx&0xf0000000)>>28;
    if (idx>1) nc++; // Take only SSD and SDD
  }

  Int_t swap;//stupid sorting
  do {
    swap=0;
    for (i=0; i<nc-1; i++) {
      if (fdEdxSample[i]<=fdEdxSample[i+1]) continue;
      Float_t tmp=fdEdxSample[i];
      fdEdxSample[i]=fdEdxSample[i+1]; fdEdxSample[i+1]=tmp;
      swap++;
    }
  } while (swap);

  Int_t nl=Int_t(low*nc), nu=Int_t(up*nc); //b.b. to take two lowest dEdX
                                           // values from four ones choose
                                           // nu=2
  Float_t dedx=0;
  for (i=nl; i<nu; i++) dedx += fdEdxSample[i];
  if (nu-nl>0) dedx /= (nu-nl);

  SetdEdx(dedx);
}

Double_t AliITStrackV2::GetBz() const {
  //
  // returns Bz component of the magnetic field (kG)
  //
  if (AliTracker::UniformField()) return AliTracker::GetBz();
  Double_t r[3]; GetXYZ(r); 
  return AliTracker::GetBz(r);
}

//____________________________________________________________________________
Bool_t AliITStrackV2::
GetPhiZat(Double_t rk, Double_t &phik, Double_t &zk) const {
  //------------------------------------------------------------------
  // This function returns the global cylindrical (phik,zk) of the track 
  // position estimated at the radius rk. 
  // The track curvature is neglected.
  //------------------------------------------------------------------
  Double_t d=GetD(0.,0.);
  if (TMath::Abs(d) > rk) return kFALSE; 

  Double_t r=TMath::Sqrt(GetX()*GetX() + GetY()*GetY());
  Double_t phi=GetAlpha()+TMath::ASin(GetSnp());

  phik=phi+TMath::ASin(d/rk)-TMath::ASin(d/r);
  zk=GetZ()+GetTgl()*(TMath::Sqrt(rk*rk-d*d) - TMath::Sqrt(r*r-d*d));

  return kTRUE;
}