EvtSLN.cc

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//--------------------------------------------------------------------------
//
// 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: EvtSLN.cc
//
// Description: B ==> tau + nu
//
// Modification history:
//
//    RYD/SHY   April 23, 1997           Module created
//
//------------------------------------------------------------------------
//
#include "EvtSLN.hh"
#include "../EvtGenBase/EvtDiracSpinor.hh"
#include "../EvtGenBase/EvtGenKine.hh"
#include "../EvtGenBase/EvtPDL.hh"
#include "../EvtGenBase/EvtParticle.hh"
#include "../EvtGenBase/EvtPatches.hh"
#include "../EvtGenBase/EvtReport.hh"
#include "../EvtGenBase/EvtVector4C.hh"
#include <iostream>
#include <stdlib.h>
#include <string>
 
EvtSLN::~EvtSLN() {}
 
void EvtSLN::getName( std::string& model_name ) { model_name = "SLN"; }
 
EvtDecayBase* EvtSLN::clone() { return new EvtSLN; }
 
void EvtSLN::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::SCALAR );
 
  checkSpinDaughter( 0, EvtSpinType::DIRAC );
  checkSpinDaughter( 1, EvtSpinType::NEUTRINO );
}
 
void EvtSLN::initProbMax() {
 
  double M = EvtPDL::getMeanMass( getParentId() );
  double m = EvtPDL::getMeanMass( getDaug( 0 ) );
 
  double probMax = 8.0 * ( M * M - m * m ) * m * m;
 
  setProbMax( probMax );
}
 
void EvtSLN::decay( EvtParticle* p ) {
 
  static EvtId EM   = EvtPDL::getId( "e-" );
  static EvtId MUM  = EvtPDL::getId( "mu-" );
  static EvtId TAUM = EvtPDL::getId( "tau-" );
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  EvtParticle *l, *nul;
  l   = p->getDaug( 0 );
  nul = p->getDaug( 1 );
 
  EvtVector4R p4_p;
  p4_p.set( p->mass(), 0.0, 0.0, 0.0 );
 
  EvtVector4C l1, l2;
 
  if ( getDaug( 0 ) == TAUM || getDaug( 0 ) == MUM || getDaug( 0 ) == EM )
  {
    l1 = EvtLeptonVACurrent( l->spParent( 0 ), nul->spParentNeutrino() );
    l2 = EvtLeptonVACurrent( l->spParent( 1 ), nul->spParentNeutrino() );
  }
  else
  {
    l1 = EvtLeptonVACurrent( nul->spParentNeutrino(), l->spParent( 0 ) );
    l2 = EvtLeptonVACurrent( nul->spParentNeutrino(), l->spParent( 1 ) );
  }
 
  vertex( 0, p4_p * l1 );
  vertex( 1, p4_p * l2 );
 
  return;
}