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[u/mrichter/AliRoot.git] / PWG2 / RESONANCES / AliRsnMother.cxx

//
// Class AliRsnMother
//
// Implementation of a pair of tracks, for several purposes
// - computing the total 4-momentum & inv. mass for output histos filling
// - evaluating cut checks on the pair of particles
// - evaluating any kind of kinematic value over their sum
//
// authors: Martin Vala (martin.vala@cern.ch)
//          Alberto Pulvirenti (alberto.pulvirenti@ct.infn.it)
//
#include <Riostream.h>
#include <TVector3.h>
#include "AliAODMCParticle.h"
#include "AliMCParticle.h"
#include "AliRsnDaughter.h"
#include "AliRsnPairDef.h"
#include "AliRsnMother.h"

ClassImp(AliRsnMother)

//_____________________________________________________________________________
AliRsnMother::AliRsnMother() : 
  fUseMC(kFALSE),
  fSum(),
  fSumMC()
{
//
// Constructor.
// Initializes all variables to meaningless values.
//

  Int_t i;
  for (i = 0; i < 2; i++) fDaughter[i] = 0x0;
}

//_____________________________________________________________________________
AliRsnMother::AliRsnMother(const AliRsnMother &obj) : 
  TObject(obj), 
  fUseMC(obj.fUseMC),
  fSum(obj.fSum),
  fSumMC(obj.fSumMC)
{
//
// Copy constructor.
// Initializes all variables to copy values.
// Does not duplicate pointers.
//

  Int_t i;
  for (i = 0; i < 2; i++) fDaughter[i] = obj.fDaughter[i];
}

//_____________________________________________________________________________
AliRsnMother& AliRsnMother::operator=(const AliRsnMother &obj)
{
//
// Assignment operator.
// Initializes all variables to copy values.
// Does not duplicate pointers.
//

  Int_t i;
  
  fSum = obj.fSum;
  fSumMC = obj.fSumMC;
  
  for (i = 0; i < 2; i++) fDaughter[i] = obj.fDaughter[i];

  return (*this);
}

//_____________________________________________________________________________
AliRsnMother::~AliRsnMother()
{
//
// Desctructor.
// Does nothing, since pointers are not created in this class.
//
}

//_____________________________________________________________________________
Int_t AliRsnMother::CommonMother(Int_t &m0, Int_t &m1) const
{
//
// Checks if the two tracks in the pair have the same mother.
// This can be known if MC info is present.
// If the mother label is the same, rhe PDG code of the mother is returned,
// otherwise the method returns 0.
// In the two arguments passed by reference, the mothers of the two daghters are stored
//

  // if MC info is not available, the pairs is not true by default
  if (!fDaughter[0]->GetRefMC() || !fDaughter[1]->GetRefMC()) 
  {
    AliInfo("Cannot know if the pairs is true or not because MC Info is not present");
    return 0;
  }

  // check that labels are the same
  m0 = -1;
  m1 = -2;
  if (fDaughter[0]->IsESD() && fDaughter[1]->IsESD() )
  {
    if (fDaughter[0]->GetRefMCESD() && fDaughter[1]->GetRefMCESD())
    {
      m0 = fDaughter[0]->GetRefMCESD()->Particle()->GetFirstMother();
      m1 = fDaughter[1]->GetRefMCESD()->Particle()->GetFirstMother();
    }
  }
  if (fDaughter[0]->IsAOD() && fDaughter[1]->IsAOD())
  {
    if (fDaughter[0]->GetRefMCAOD() && fDaughter[1]->GetRefMCAOD())
    {
      m0 = fDaughter[0]->GetRefMCAOD()->GetMother();
      m1 = fDaughter[1]->GetRefMCAOD()->GetMother();
    }
  }
  if (m0 != m1) return 0;

  // if we reach this point, the two tracks have the same mother
  // let's check now the PDG code of this common mother
  return TMath::Abs(fDaughter[0]->GetMotherPDG());
}

//_____________________________________________________________________________
void AliRsnMother::SetDaughters
(AliRsnDaughter *d0, Double_t mass0, AliRsnDaughter *d1, Double_t mass1)
{
//
// Sets the pair defined in this usind tso passed daughters and two masses
// which will be assigned to them, in order to recompute their 4-momenta
// and sum them into the datamembers of this object.
//

  if (d0) fDaughter[0] = d0;
  if (d1) fDaughter[1] = d1;
  
  if (!d0 || !d1) return;
  
  fDaughter[0]->SetMass(mass0);
  fDaughter[1]->SetMass(mass1);
  
  fSum   = fDaughter[0]->P(kFALSE) + fDaughter[1]->P(kFALSE);
  fSumMC = fDaughter[0]->P(kTRUE)  + fDaughter[1]->P(kTRUE);
}

//_____________________________________________________________________________
void AliRsnMother::ResetPair()
{
//
// Resets the mother, nullifying all data members
//

  Int_t i;
  for (i = 0; i < 2; i++) fDaughter[i] = 0x0;
  
  fSum  .SetXYZM(0.0, 0.0, 0.0, 0.0);
  fSumMC.SetXYZM(0.0, 0.0, 0.0, 0.0);
}

//_____________________________________________________________________________
Double_t AliRsnMother::CosThetaStar(Bool_t first, Bool_t useMC)
{
  TLorentzVector mother    = (useMC ? fSumMC : fSum);
  TLorentzVector daughter0 = (first ? fDaughter[0]->P() : fDaughter[1]->P());
  TLorentzVector daughter1 = (first ? fDaughter[1]->P() : fDaughter[0]->P());
  TVector3 momentumM          (mother.Vect());
  TVector3 normal             (mother.Y()/momentumM.Mag(), -mother.X()/momentumM.Mag(), 0.0);

  // Computes first the invariant mass of the mother
  Double_t mass0            = fDaughter[0]->P().M();
  Double_t mass1            = fDaughter[1]->P().M();
  Double_t p0               = daughter0.Vect().Mag();
  Double_t p1               = daughter1.Vect().Mag();
  Double_t E0               = TMath::Sqrt(mass0*mass0+p0*p0);
  Double_t E1               = TMath::Sqrt(mass1*mass1+p1*p1);
  Double_t MotherMass       = TMath::Sqrt((E0+E1)*(E0+E1)-(p0*p0+2.0*daughter0.Vect().Dot(daughter1.Vect())+p1*p1));
  MotherMass = fSum.M();

  // Computes components of beta
  Double_t betaX = -mother.X()/mother.E();
  Double_t betaY = -mother.Y()/mother.E();
  Double_t betaZ = -mother.Z()/mother.E();

  // Computes Lorentz transformation of the momentum of the first daughter
  // into the rest frame of the mother and theta*
  daughter0.Boost(betaX,betaY,betaZ);
  TVector3 momentumD = daughter0.Vect();

  Double_t cosThetaStar = normal.Dot(momentumD)/momentumD.Mag();

  return cosThetaStar;
}

//_____________________________________________________________________________
void AliRsnMother::PrintInfo(const Option_t * /*option*/) const
{
//
// Print some info of the pair.
// The options are passed to the AliRsnDaughter::Print() method
//

  AliInfo("======== BEGIN PAIR INFO ===========");
  AliInfo("Track #1");
  fDaughter[0]->Print();
  AliInfo("Track #2");
  fDaughter[1]->Print();
  AliInfo("========= END PAIR INFO ===========");
}

//_____________________________________________________________________________
Bool_t AliRsnMother::CheckPair() const
{
//
// Checks that the pair is well initialized:
// - both daughters are good pointers
// - if MC is required, both daughters have a MC reference
//

  if (!fDaughter[0] || !fDaughter[1]) 
  {
    AliError("One of the two tracks is NULL in this pair!");
    return kFALSE;
  }
  
  if (fUseMC)
  {
    if (fDaughter[0]->GetRefMC() == 0x0 || fDaughter[1]->GetRefMC() == 0x0)
    {
      AliError("Required MC info but not all MC refs are available");
      return kFALSE;
    }
  }
  
  return kTRUE;
}

//_____________________________________________________________________________
Bool_t AliRsnMother::MatchesDef(AliRsnPairDef *def)
{
//
// Checks if the daughters, in any order, do match a given decay channel,
// using the specified identification method, which can be the 'true' one
// or the 'realistic' one only.
//

  if (!def) return kFALSE;
  if (!fDaughter[0]->GetRefMC()) return kFALSE;
  if (!fDaughter[1]->GetRefMC()) return kFALSE;

  Bool_t decayMatch = kFALSE;
  Int_t  pdg[2], ref[2];
  pdg[0] = fDaughter[0]->GetPDG();
  pdg[1] = fDaughter[1]->GetPDG();
  ref[0] = TMath::Abs(AliPID::ParticleCode(def->GetPID(0)));
  ref[1] = TMath::Abs(AliPID::ParticleCode(def->GetPID(1)));

  // check #1:
  // if first member of pairDef has same sign as first member of this,
  // daughter[0] perfect PID must match first member of pairDef
  // daughter[1] perfect PID must march second member of pairDef
  if (fDaughter[0]->IsSign(def->GetCharge(0)) && fDaughter[1]->IsSign(def->GetCharge(1))) 
  {
    decayMatch = (pdg[0] == ref[0] && pdg[1] == ref[1]);
  }

  // check #2:
  // if first member of pairDef has same sign as second member of this,
  // daughter[0] perfect PID must match second member of pairDef
  // daughter[1] perfect PID must march first member of pairDef
  if (fDaughter[1]->IsSign(def->GetCharge(0)) && fDaughter[0]->IsSign(def->GetCharge(1))) 
  {
    decayMatch = (pdg[0] == ref[1] && pdg[1] == ref[0]);
  }

  return (decayMatch && (CommonMother() == def->GetMotherPDG()));
}