MpdDecayerPyt8.h

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// -------------------------------------------------------------------------
// -----                 MpdDecayerPyt8 header file                    -----
// -----                      Created 23/07/2020                       -----
// -----                          A. Zinchenko                         -----
// -----             External decayer for MPD using Pythia8            -----
// -----                (adapted from TPythia8Decayer)                 -----
// -------------------------------------------------------------------------
 
#ifndef MPDDECAYERPYT8_H
#define MPDDECAYERPYT8_H
 
#include <Pythia8/Pythia.h>
#include <TLorentzVector.h>
#include <TRotation.h>
#include <TVirtualMCDecayer.h>
 
class TClonesArrray;
class TObjArrray;
class TParticle;
class TPythia8;
class TRandom;
 
#include <set>
#if PYTHIA_VERSION_INTEGER < 8304
typedef Pythia8::ParticleDataEntry* ParticleDataEntryPtr;
#else
typedef Pythia8::ParticleDataEntryPtr ParticleDataEntryPtr;
#endif
 
class MpdDecayerPyt8 : public TVirtualMCDecayer
{
 
  public:
    enum SourceFlag
    {
        kPythia,
        kCustom
    };   // particle container source
 
    virtual ~MpdDecayerPyt8() { ; }
 
    virtual void Init();
    virtual void Decay(Int_t pdg, TLorentzVector* p);
    virtual Int_t ImportParticles(TClonesArray* particles);
    virtual void SetForceDecay(Int_t type);
    virtual void ForceDecay();
    virtual Float_t GetPartialBranchingRatio(Int_t ipart);
    virtual Float_t GetLifetime(Int_t kf);
    virtual void ReadDecayTable();
 
    virtual void SetDebugLevel(Int_t debug) { fDebug = debug; }
    virtual void SetGlobalPolar(Int_t glob = 1) { fGlobalPolar = glob; }
 
    static MpdDecayerPyt8* Instance();
    void Decay(TParticle* part);
    void AddMotherPdg(Int_t pdg);
    // using   TPythia8Decayer::Decay; // makes base class function visible
 
  protected:
    MpdDecayerPyt8();
    void AppendParticle(Int_t pdg, TLorentzVector* p);
    void ClearEvent();
 
  private:
    void Gdecay(Int_t idpart, TLorentzVector* p);
    void Gdeca2(Double_t xm0, Double_t xm1, Double_t xm2, Double_t pcm[2][4]);
    // void Anisotropy (Double_t* pvert, Double_t *rndm, Double_t polar, Double_t &phi, Double_t &costh);
    void Anisotropy(Double_t* pvert, Double_t* rndm, TVector3& polar, Double_t& phi, Double_t& costh);
    void ChangeBranchings();
    void ChangeParticleBr(TObjArray* tokens, Bool_t exclusive);
 
    static MpdDecayerPyt8* fgInstance;   // singleton instance
 
    TPythia8* fPythia8;   // Pointer to pythia8
    Int_t fDebug;         // Debug level
    Int_t fGlobalPolar;   // global polarization flag
 
    Float_t fBranch;                // branching of lambda to p + \pi-
    ParticleDataEntryPtr fLambda;   // pointer to Lambda in Pythia8 database
    TLorentzVector fMother;         // mother decay point position
    TClonesArray* fParticles;
    TRotation fRotation;
    SourceFlag fSourceFlag;
    std::set<Int_t> fMothersPdg;
    TRandom* fRandom;
 
    ClassDef(MpdDecayerPyt8, 0);   // MPD Particle Decayer using Pythia8
};
#endif