include/EvtGenModels/EvtVubHybrid.hh

0001
0002 /***********************************************************************
0003 * Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
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0020
0021 #ifndef EVTVUBHYBRID_HH
0022 #define EVTVUBHYBRID_HH
0023
0024 #include "EvtGenBase/EvtDecayIncoherent.hh"
0025
0026 #include "EvtGenModels/EvtVubdGamma.hh"
0027
0028 #include <memory>
0029 #include <vector>
0030
0031 class EvtParticle;
0032 class RandGeneral;
0033
0034 // Description:
0035 // Class to generate inclusive B to X_u l nu decays.
0036 // This class is based on EvtVub by Sven Menke with an update to
0037 // generate the inclusive decays in such a way that the right
0038 // mix of inclusive and exclusive decays is obtained:
0039 // "Hybrid Model" by Dominique Fortin.
0040 // NOTE:
0041 // - A set of weights (for bins in the kinematic variables mX, q2, El)
0042 //   is read from DECAY.DEC. This set of weights must be consistent
0043 //   with the other parameters specified (excl. BF, non-res BF, mb, a).
0044 // - If no binning/weights are specified in DECAY.DEC the hybrid
0045 //   reweighting is not activated
0046
0047 class EvtVubHybrid : public EvtDecayIncoherent {
0048   public:
0049     std::string getName() override;
0050
0051     EvtDecayBase* clone() override;
0052
0053     void initProbMax() override;
0054
0055     void init() override;
0056
0057     void decay( EvtParticle* p ) override;
0058
0059     void readWeights( int startArg = 0 );
0060
0061     double getWeight( double mX, double q2, double El );
0062
0063   private:
0064     double findPFermi();
0065
0066     enum
0067     {
0068         nParameters = 3,
0069         nVariables = 3
0070     };
0071
0072     bool _noHybrid =
0073         false;    // _noHybrid will be set TRUE if the DECAY.DEC file has no binning or weights
0074     bool _storeQplus =
0075         true;    // _storeQplus should alwasy be TRUE: writes out Fermi motion parameter
0076
0077     double _mb = 4.62;        // the b-quark pole mass in GeV (try 4.65 to 4.9)
0078     double _a = 2.27;         // Parameter for the Fermi Motion (1.29 is good)
0079     double _alphas = 0.22;    // Strong Coupling at m_b (around 0.24)
0080     double _dGMax = 3.;       // max dGamma*p2 value;
0081     int _nbins = 0;
0082     double _masscut = 0.28;
0083     std::vector<double> _bins_mX;
0084     std::vector<double> _bins_q2;
0085     std::vector<double> _bins_El;
0086     std::vector<double> _weights;
0087     std::unique_ptr<EvtVubdGamma> _dGamma;    // calculates the decay rate
0088     std::vector<double> _pf;
0089 };
0090
0091 #endif