//--------------------------------------------------------------------------
//
// 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) 1998      Caltech, UCSB
//
// Module: EvtSll.cc
//
// Description: The decay of a scalar meson to two leptons,
//              or generally, two spin 1/2 particles.
//              E.g., B0 -> tau+ tau-
//
// Modification history:
//
//    SHY       April 23, 1997       Module created
//
//------------------------------------------------------------------------
//
#include "EvtGenBase/EvtPatches.hh"
#include <stdlib.h>
#include <iostream>
#include <string>
#include "EvtGenBase/EvtParticle.hh"
#include "EvtGenBase/EvtPDL.hh"
#include "EvtGenBase/EvtGenKine.hh"
#include "EvtGenModels/EvtSll.hh"
#include "EvtGenBase/EvtDiracSpinor.hh"
#include "EvtGenBase/EvtReport.hh"
#include "EvtGenBase/EvtVector4C.hh"

EvtSll::~EvtSll() {}

std::string EvtSll::getName(){

  return "SLL";     

}


EvtDecayBase* EvtSll::clone(){

  return new EvtSll;

}

void EvtSll::init(){

  // check that there are 0 arguments
  checkNArg(0);
  checkNDaug(2);

  checkSpinParent(EvtSpinType::SCALAR);

  checkSpinDaughter(0,EvtSpinType::DIRAC);
  checkSpinDaughter(1,EvtSpinType::DIRAC);

}

void EvtSll::decay(EvtParticle *p){


  p->initializePhaseSpace(getNDaug(),getDaugs());

  EvtParticle *l1, *l2;
  l1 = p->getDaug(0);
  l2 = p->getDaug(1);
  EvtVector4R p4_p;
  p4_p.set(p->mass(),0.0,0.0,0.0);

  EvtVector4C l11, l12, l21, l22;
  
  l11=EvtLeptonVACurrent(l1->spParent(0),l2->spParent(0));
  l12=EvtLeptonVACurrent(l1->spParent(0),l2->spParent(1));
  l21=EvtLeptonVACurrent(l1->spParent(1),l2->spParent(0));
  l22=EvtLeptonVACurrent(l1->spParent(1),l2->spParent(1));

  vertex(0,0,p4_p*l11);
  vertex(0,1,p4_p*l12);
  vertex(1,0,p4_p*l21);
  vertex(1,1,p4_p*l22);
  
  return;

}