TauolaParticlePair.h

#ifndef _TauolaParticlePair_h_included_
#define _TauolaParticlePair_h_included_

#include <iostream>
#include <vector>
#include <math.h>
#include "TauolaParticle.h"

// Forward declarations for friend function
namespace TauSpinner {
  class SimpleParticle;
  extern double getLongitudinalPolarization(double,SimpleParticle&,SimpleParticle&);
}

namespace Tauolapp
{

class TauolaParticlePair{

 public:

  // needed to access m_R matrix and recalculateRij() function.
  friend class Plots;
  friend double TauSpinner::getLongitudinalPolarization(double,TauSpinner::SimpleParticle&,TauSpinner::SimpleParticle&);

  TauolaParticlePair(std::vector<TauolaParticle*> &particle_list);

  void decayTauPair();

  bool contains(TauolaParticle * particle);

  TauolaParticle * getTauPlus(std::vector<TauolaParticle*> particles);

  TauolaParticle * getTauMinus(std::vector<TauolaParticle*> particles);

  TauolaParticle * getGrandmotherPlus(std::vector<TauolaParticle*> particles);

  TauolaParticle * getGrandmotherMinus(std::vector<TauolaParticle*> particles);

  void print();

  void checkMomentumConservation();

 private:

  TauolaParticlePair() {}

  static void setBornKinematics(int  incoming_pdg_id, int  outgoing_pdg_id, double  invariant_mass_squared, double  cosTheta);

  std::vector<TauolaParticle*> m_final_particles;
  
  std::vector<TauolaParticle*> m_production_particles;
  
  TauolaParticle* m_mother;

  bool m_mother_exists;
  
  std::vector<TauolaParticle*> m_grandmothers;

  void recalculateRij(int incoming_pdg_id, int outgoing_pdg_id, double invariant_mass_squared, double cosTheta);

  void rotateSystem(vector<TauolaParticle *> grandmothers,
                    vector<TauolaParticle *> taus,
                    double theta,
                    int axis, 
                    int axis2=TauolaParticle::Z_AXIS);


  void boostFromLabToTauPairFrame(double * rotation_angle1, 
                                  double * rotation_angle2,
                                  double * rotation_angle3,
                                  TauolaParticle * mother,
                                  vector<TauolaParticle *> grandmothers,
                                  vector<TauolaParticle *> taus);

  void boostFromTauPairToLabFrame(double rotation_angle1, 
                                  double rotation_angle2,
                                  double rotation_angle3,
                                  TauolaParticle * mother,
                                  vector<TauolaParticle *> grandmothers,
                                  vector<TauolaParticle *> taus);
    
  void initializeDensityMatrix();

  TauolaParticle * makeTemporaryMother(vector<TauolaParticle *> taus);

  //void ANGULU(int *IDE, int *IDF, double *SVAR, double *COSTHE);
  double getZPolarization(int *incoming_pdg_id,
                          int *outgoing_pdg_id, 
                          double *invMass,
                          double *cosTheta);

  double getVirtuality(TauolaParticle * p1, TauolaParticle*p2, bool flip);

  void addToBeam(TauolaParticle * pcle,
                 std::vector<TauolaParticle*> * candidates_same,
                 std::vector<TauolaParticle*> * candidates_opp);
    

  double m_R[4][4]; //density matrix
};

//Temporary
//Pz is still calculated using the FORTRAN routine in tauola_extra.f
//This should be migrated to C++ at some stage.
extern "C" {
  extern double plzap0_(int *incoming_pdg_id,
                        int *outgoing_pdg_id, 
                        double *invMass,
                        double *cosTheta);
}

} // namespace Tauolapp
#endif