include/EvtGenModels/EvtVubdGamma.hh

0001
0002 /***********************************************************************
0003 * Copyright 1998-2020 CERN for the benefit of the EvtGen authors       *
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0014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
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0016 *                                                                      *
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0020
0021 #ifndef EVTVUBDGAMMA_HH
0022 #define EVTVUBDGAMMA_HH
0023
0024 // Description:
0025 //    3                                         2                2
0026 //   d Gamma                 /   _      _ _2  mb           _2  mb
0027 //  ---------- = 12 Gamma   | (1+x-z)(z-x-p ) -- W  + (1-z+p ) -- W
0028 //         _ 2           0   \                 2  1             2  2
0029 //  dx dz dp                                   2
0030 //                                _   _  _2  mb                 2   \.
0031 //                             + [x(z-x)-p ] -- (W + 2mb W  + mb W ) |
0032 //                                            4   3       4       5 /
0033 //
0034 //   with
0035 //        2 E           2
0036 //           l    _2   p        2 v.p    _
0037 //   x = ------ , p = --- , z = ------ , x = 1-x
0038 //         mb           2         mb
0039 //                    mb
0040 //
0041 //   the triple differential decay rate according to
0042 //   hep-ph/9905351 v2
0043
0044 class EvtVubdGamma final {
0045   public:
0046     // Constructors
0047
0048     EvtVubdGamma( const double& alphas );
0049
0050     // Operators
0051
0052     // Selectors
0053
0054     // Modifiers
0055
0056     // Methods
0057
0058     double getdGdxdzdp( const double& x, const double& z, const double& p2 );
0059
0060   protected:
0061     // Helper functions
0062
0063     double delta( const double& x, const double& xmin, const double& xmax );
0064
0065     double getW1nodelta( const double& x, const double& z, const double& p2 );
0066
0067     double getW2nodelta( const double& x, const double& z, const double& p2 );
0068
0069     double getW3nodelta( const double& x, const double& z, const double& p2 );
0070
0071     double getW4nodelta( const double& x, const double& z, const double& p2 );
0072
0073     double getW5nodelta( const double& x, const double& z, const double& p2 );
0074
0075     double getW1delta( const double& x, const double& z );
0076
0077     double getW4plus5delta( const double& x, const double& z );
0078
0079   private:
0080     // Friends
0081
0082     // Data members
0083
0084     double _alphas;
0085     double _epsilon1;
0086     double _epsilon2;
0087     double _epsilon3;
0088 };
0089
0090 #endif    // EVTVUBDGAMMA_HH