PairAnalysisPair.cxx

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//
//
// Authors:
//   Julian Book   <Julian.Book@cern.ch>
/*
 
  PairAnalysis pair interface class.
 
*/
//                                                                       //
 
 
#include <TDatabasePDG.h>
 
#include "CbmVertex.h"
 
#include "PairAnalysisPair.h"
#include "PairAnalysisTrack.h"
 
ClassImp(PairAnalysisPair)
 
  Double_t PairAnalysisPair::fBeamEnergy = -1.;
 
PairAnalysisPair::PairAnalysisPair() : PairAnalysisTrack(), fRefD1(), fRefD2() {
  //
  // Default Constructor
  //
}
 
//______________________________________________
PairAnalysisPair::PairAnalysisPair(const PairAnalysisPair& pair)
  : PairAnalysisTrack(pair)
  , fType(pair.GetType())
  , fCharge(pair.Charge())
  , fLabel(pair.GetLabel())
  , fWeight(pair.GetWeight())
  , fPdgCode(pair.PdgCode())
  , fRefD1(pair.GetFirstDaughter())
  , fRefD2(pair.GetSecondDaughter())
  , fPid1(pair.GetFirstDaughterPid())
  , fPid2(pair.GetSecondDaughterPid())
  , fKFUsage(pair.GetKFUsage()) {
  //
  // Copy Constructor
  //
}
 
//______________________________________________
PairAnalysisPair::PairAnalysisPair(Char_t type)
  : fType(type), fRefD1(), fRefD2() {
  //
  // Constructor with type
  //
}
 
//______________________________________________
PairAnalysisPair::~PairAnalysisPair() {
  //
  // Default Destructor
  //
}
 
//______________________________________________
void PairAnalysisPair::GetThetaPhiCM(TLorentzVector& motherMom,
                                     TLorentzVector& p1Mom,
                                     TLorentzVector& p2Mom,
                                     Double_t& thetaHE,
                                     Double_t& phiHE,
                                     Double_t& thetaCS,
                                     Double_t& phiCS) const {
  //
  // Calculate theta and phi in helicity and Collins-Soper coordinate frame
  //
 
  const Double_t proMass = TDatabasePDG::Instance()->GetParticle(2212)->Mass();
  TLorentzVector projMom(
    0.,
    0.,
    fBeamEnergy,
    TMath::Sqrt(fBeamEnergy * fBeamEnergy + proMass * proMass));
  TLorentzVector targMom(0., 0., 0., TMath::Sqrt(0. * 0 + proMass * proMass));
 
  // boost all the 4-mom vectors to the mother rest frame
  TVector3 beta = (-1.0 / motherMom.E()) * motherMom.Vect();
  p1Mom.Boost(beta);
  p2Mom.Boost(beta);
  projMom.Boost(beta);
  targMom.Boost(beta);
 
  // x,y,z axes
  TVector3 zAxisHE = (motherMom.Vect()).Unit();
  TVector3 zAxisCS = ((projMom.Vect()).Unit() - (targMom.Vect()).Unit()).Unit();
  TVector3 yAxis   = ((projMom.Vect()).Cross(targMom.Vect())).Unit();
  TVector3 xAxisHE = (yAxis.Cross(zAxisHE)).Unit();
  TVector3 xAxisCS = (yAxis.Cross(zAxisCS)).Unit();
 
  // fill theta and phi
  if (static_cast<PairAnalysisTrack*>(fRefD1.GetObject())->Charge() > 0) {
    thetaHE = zAxisHE.Dot((p1Mom.Vect()).Unit());
    thetaCS = zAxisCS.Dot((p1Mom.Vect()).Unit());
    phiHE =
      TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxisHE));
    phiCS =
      TMath::ATan2((p1Mom.Vect()).Dot(yAxis), (p1Mom.Vect()).Dot(xAxisCS));
  } else {
    thetaHE = zAxisHE.Dot((p2Mom.Vect()).Unit());
    thetaCS = zAxisCS.Dot((p2Mom.Vect()).Unit());
    phiHE =
      TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxisHE));
    phiCS =
      TMath::ATan2((p2Mom.Vect()).Dot(yAxis), (p2Mom.Vect()).Dot(xAxisCS));
  }
}
 
//______________________________________________
Double_t PairAnalysisPair::GetCosPointingAngle(const CbmVertex* primVtx) const {
  //
  // Calculate the poiting angle of the pair to the primary vertex and take the cosine
  //
  if (!primVtx) return -1.;
 
  TVector3 pairPos(Xv(), Yv(), Zv());
  TVector3 pvtxPos;
  primVtx->Position(pvtxPos);
  pairPos -= pvtxPos;  //vector between the reference point and the V0 vertex
 
  TVector3 pairMom(Px(), Py(), Pz());
  Double_t pointingAngle = pairMom.Angle(pairPos);
  return TMath::Abs(TMath::Cos(pointingAngle));
}
 
//______________________________________________
void PairAnalysisPair::GetDCA(const CbmVertex* primVtx,
                              Double_t d0z0[2]) const {
  //
  // Calculate the dca of the mother with respect to the primary vertex
  //
  if (!primVtx) return;
 
  d0z0[0] = TMath::Sqrt(TMath::Power(Xv() - primVtx->GetX(), 2)
                        + TMath::Power(Yv() - primVtx->GetY(), 2));
 
  d0z0[1] = Zv() - primVtx->GetZ();
  return;
}
 
//______________________________________________
void PairAnalysisPair::SetBeamEnergy(Double_t beamEbyHand) {
  //
  // set the beam energy by hand
  //
  fBeamEnergy = beamEbyHand;
}