include/EvtGenModels/EvtBLLNuLAmp.hh

0001
0002 /***********************************************************************
0003 * Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
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0020
0021 #ifndef EVTBLLNUL_AMP_HH
0022 #define EVTBLLNUL_AMP_HH
0023
0024 #include "EvtGenBase/EvtAmp.hh"
0025 #include "EvtGenBase/EvtComplex.hh"
0026 #include "EvtGenBase/EvtId.hh"
0027 #include "EvtGenBase/EvtTensor4C.hh"
0028 #include "EvtGenBase/EvtVector4R.hh"
0029
0030 #include <vector>
0031
0032 class EvtParticle;
0033
0034 // Description: Header file for the amplitude calculation for the "BLLNUL"
0035 //              model which generates rare four-leptonic B-decays
0036 //              B^-(p) -> ell^+(k_1) ell^-(k_2) neu (k_3) ell^-(k_4)
0037
0038 class EvtBLLNuLAmp {
0039   public:
0040     EvtBLLNuLAmp( double Vub = 4.09e-3 );
0041     EvtBLLNuLAmp( double qSqMin, double kSqMin, bool symmetry,
0042                   double Vub = 4.09e-3 );
0043
0044     void CalcAmp( EvtParticle* parent, EvtAmp& amp ) const;
0045     void setParameters( double qSqMin, double kSqMin, bool symmetry );
0046
0047     // Resonance poles
0048     class ResPole final {
0049       public:
0050         ResPole( double mass, double width, double coupling );
0051
0052         EvtComplex propagator( double qSq, int numForm = 0 ) const;
0053
0054         double getMass() const { return m0_; }
0055         double getMassSq() const { return m0Sq_; }
0056         double getWidth() const { return w0_; }
0057         double getCoupling() const { return c_; }
0058
0059       private:
0060         double m0_;    // pole mass
0061         double m0Sq_;
0062         double w0_;    // width
0063         double c_;     // coupling constant
0064         EvtComplex I_;
0065         EvtComplex Imw_;
0066     };
0067
0068   protected:
0069     EvtTensor4C getHadronTensor( const EvtVector4R& q, const EvtVector4R& k,
0070                                  const double qSq, const double kSq,
0071                                  const double MB, const int sign ) const;
0072
0073     std::vector<EvtComplex> getVMDTerms( double qSq, double kSq, double MB ) const;
0074
0075     EvtComplex getBStarTerm( double qSq, double kSq, double MB ) const;
0076
0077     double FF_B2Bstar( double qSq ) const;
0078
0079     double FF_V( double kSq ) const;
0080
0081     double FF_A1( double kSq ) const;
0082
0083     double FF_A2( double kSq ) const;
0084
0085   private:
0086     // Kinematic cut-offs
0087     double qSqMin_;
0088     double kSqMin_;
0089
0090     // If we have identical charged lepton flavours
0091     bool symmetry_;
0092
0093     // B+, B- Ids
0094     EvtId BpId_, BnId_;
0095
0096     // Form factor constants
0097     double coupling_, sqrt2_;
0098     double fBu_;
0099
0100     // Resonance poles
0101     EvtBLLNuLAmp::ResPole Bstar_, Upsilon_;
0102
0103     std::vector<EvtBLLNuLAmp::ResPole> resPoles_;
0104     int nPoles_;
0105
0106     // Complex number constants
0107     EvtComplex zero_, unitI_;
0108 };
0109
0110 inline void EvtBLLNuLAmp::setParameters( double qSqMin, double kSqMin,
0111                                          bool symmetry )
0112 {
0113     qSqMin_ = qSqMin;
0114     kSqMin_ = kSqMin;
0115     symmetry_ = symmetry;
0116 }
0117
0118 #endif