//--------------------------------------------------------------------------
//
// Environment:
//      This software is part of the EvtGen package developed jointly
//      for the BaBar and CLEO collaborations.  If you use all or part
//      of it, please give an appropriate acknowledgement.
//
// Copyright Information: See EvtGen/COPYRIGHT
//      Copyright (C) 2003      Caltech
//
// Module: EvtGen/EvtRadiativeBaryonicPenguins.hh
//
// Description:Implementation of the decay B- -> lambda p_bar gamma according to
// Cheng, Yang; hep-ph/0201015
//
// Modification history:
//
//    JFS     December 16th, 2003         Module created
//
//------------------------------------------------------------------------

#ifndef EVTLAMBDAPBARGAMMA_HH
#define EVTLAMBDAPBARGAMMA_HH

#include "EvtGenBase/EvtDecayAmp.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtComplex.hh"
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtConst.hh"

class EvtLambdaP_BarGamma : public EvtDecayAmp {

public:
        
  EvtLambdaP_BarGamma();
  ~EvtLambdaP_BarGamma() {;}
  
  std::string getName();
  EvtDecayBase* clone();
  void decay(EvtParticle* p);
  void init();
  void initProbMax();
  
private:
  // some constants to make the code easier to read and maintain
  // these three should be constants... (implementation of getMass() prohibits this)
  double _mLambdab; //  = 5.624;                          // Lambda_b mass
  double _mLambda0;  //  = 1.115684;                       // Lambda0 mass
  double _c7Eff;     //  = -0.31;                          // Wilson coefficient                                      
  double _mb;        //  =  4.4;                           // running b mass                                          
  double _mV;        //  =  5.42;                          // pole mass vector current                                
  double _mA;        //  =  5.86;                          // pole mass axial current                                 
  double _GF;        //  =  1.166E-5;                      // Fermi constant                                          
  double _gLambdab;  // =  16;                            // coupling constant Lambda_b -> B- p                         
  double _e0;        //  =  1;                             // electromagnetic coupling (+1)                           
  double _g1;        //  =  0.64;                          // heavy-light form factors at q_mSqare                    
  double _g2;        //  = -0.10;      
  double _f1;        //  =  0.64;
  double _f2;        //  = -0.31;
  double _VtbVtsStar;// = 0.038;                          // |V_tb V_ts^*|

  // user never needs to call this -> private
  // baryonic form factors f(p), g(p), at p=0
  const double f0(const double f_qm, int n=1); // calculate f(0) with f(q_max)
  const double g0(const double f_qm, int n=1); // calculate g(0) with g(q_max)
  
  // shorthand for constants a and b in the formula
  const double constA();
  const double constB();

  // 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