EvtBBScalar.hh

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#ifndef EVTBBSCALAR_HH
#define EVTBBSCALAR_HH
 
#include "EvtGenBase/EvtComplex.hh"
#include "EvtGenBase/EvtConst.hh"
#include "EvtGenBase/EvtDecayAmp.hh"
#include "EvtGenBase/EvtDiracParticle.hh"
#include "EvtGenBase/EvtId.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtScalarParticle.hh"
#include "EvtGenBase/EvtVector4C.hh"
 
#include <bitset>
#include <map>
#include <string>
#include <vector>
 
// Implementation of the decay B- -> lambda p_bar pi according to
// hep-ph/0204185, hep-ph/0211240
// This model is intended to be applicable to all decays of the type B-> baryon baryon scalar
 
class EvtBBScalar : public EvtDecayAmp {
  public:
    EvtBBScalar();
    std::string getName() const override;
    EvtBBScalar* clone() const override;
    void decay( EvtParticle* p ) override;
    void init() override;
    void initProbMax() override;
 
  private:
    struct FormFactor {
        double m_value;
        double m_sigma1;
        double m_sigma2;
        double m_mV;
    };
 
    enum Baryons
    {
        Lambda,
        Proton,
        Neutron,
        Sigma0,
        Sigma_minus,
        Xi0,
        Xi_minus,
        nBaryons
    };
 
    // used values of constants
    static const EvtComplex m_I;
    static const EvtComplex m_V_ub;
    static const EvtComplex m_V_us_star;
    static const EvtComplex m_a1;
    static const EvtComplex m_V_tb;
    static const EvtComplex m_V_ts_star;
    static const EvtComplex m_a4;
    static const EvtComplex m_a6;
 
    // used parameters in the calculation of the magnetic form factors
    static const double m_x[];
    static const double m_y[];
    // quark masses as used in the model
    static const double m_ms;
    static const double m_mu;
    static const double m_mb;
 
    // used to choose the right m_value for the form factor depending on the type of scalar
    std::string m_scalarType;
    mutable std::map<std::string, FormFactor> m_f0Map;
    mutable std::map<std::string, FormFactor> m_f1Map;
 
    // only consider F1+F2 here
    std::bitset<nBaryons> m_baryonCombination;
    void setKnownBaryonTypes( const EvtId& baryon );
 
    double B_pi_f1( double t ) const;
    double B_pi_f0( double t ) const;
    double baryonF1F2( double t ) const;
    double G_p( double t ) const;
    double G_n( double t ) const;
 
    double baryon_gA( double t ) const;
    double baryon_hA( double t ) const;
    double baryon_gP( double t ) const;
    double baryon_fS( double t ) const;
 
    double D_A( double t ) const;
    double F_A( double t ) const;
    double D_P( double t ) const;
    double F_P( double t ) const;
    double D_S( double t ) const;
    double F_S( double t ) const;
 
    // (mB1 - mB2)/(mq1 - mq1)
    double m_massRatio;
    double m_baryonMassSum;
    double formFactorFit( double t, const std::vector<double>& params ) const;
 
    static const EvtComplex m_const_B;
    static const EvtComplex m_const_C;
    const EvtVector4C amp_A( const EvtVector4R& p4B, const EvtVector4R& p4Scalar );
    const EvtComplex amp_B( const EvtDiracParticle* baryon1,
                            const EvtDiracSpinor& b1Pol,
                            const EvtDiracParticle* baryon2,
                            const EvtDiracSpinor& b2Pol, int index );
    const EvtComplex amp_B_vectorPart( const EvtDiracParticle* baryon1,
                                       const EvtDiracSpinor& b1Pol,
                                       const EvtDiracParticle* baryon2,
                                       const EvtDiracSpinor& b2Pol, int index );
    const EvtComplex amp_B_axialPart( const EvtDiracParticle* baryon1,
                                      const EvtDiracSpinor& b1Pol,
                                      const EvtDiracParticle* baryon2,
                                      const EvtDiracSpinor& b2Pol, int index );
    const EvtComplex amp_C( const EvtDiracParticle* baryon1,
                            const EvtDiracSpinor& b1Pol,
                            const EvtDiracParticle* baryon2,
                            const EvtDiracSpinor& b2Pol, int index );
    const EvtComplex amp_C_scalarPart( const EvtDiracSpinor& b1Pol,
                                       const EvtDiracSpinor& b2Pol, double t );
    const EvtComplex amp_C_pseudoscalarPart( const EvtDiracSpinor& b1Pol,
                                             const EvtDiracSpinor& b2Pol,
                                             double t );
 
    // initialize phasespace and calculate the amplitude for one (i=0,1) state of the photon
    EvtComplex calcAmpliude( const EvtParticle* p, const unsigned int polState );
};
 
#endif