EvtTaulnunu.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: EvtTaulnunu.cc
//
// Description: The leptonic decay of the tau meson.
//              E.g., tau- -> e- nueb nut
//
// Modification history:
//
//    RYD       January 17, 1997       Module created
//
//------------------------------------------------------------------------
//
#include "EvtTaulnunu.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>
 
EvtTaulnunu::~EvtTaulnunu() {}
 
void EvtTaulnunu::getName( std::string& model_name ) { model_name = "TAULNUNU"; }
 
EvtDecayBase* EvtTaulnunu::clone() { return new EvtTaulnunu; }
 
void EvtTaulnunu::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 3 );
 
  checkSpinParent( EvtSpinType::DIRAC );
 
  checkSpinDaughter( 0, EvtSpinType::DIRAC );
  checkSpinDaughter( 1, EvtSpinType::NEUTRINO );
  checkSpinDaughter( 2, EvtSpinType::NEUTRINO );
}
 
void EvtTaulnunu::initProbMax() { setProbMax( 650.0 ); }
 
void EvtTaulnunu::decay( EvtParticle* p ) {
  static EvtId TAUM = EvtPDL::getId( "tau-" );
 
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  EvtParticle *l, *nul, *nut;
 
  l   = p->getDaug( 0 );
  nul = p->getDaug( 1 );
  nut = p->getDaug( 2 );
 
  EvtVector4C l1, l2, tau1, tau2;
 
  if ( p->getId() == TAUM )
  {
 
    tau1 = EvtLeptonVACurrent( nut->spParentNeutrino(), p->sp( 0 ) );
    tau2 = EvtLeptonVACurrent( nut->spParentNeutrino(), p->sp( 1 ) );
    l1   = EvtLeptonVACurrent( l->spParent( 0 ), nul->spParentNeutrino() );
    l2   = EvtLeptonVACurrent( l->spParent( 1 ), nul->spParentNeutrino() );
  }
  else
  {
    tau1 = EvtLeptonVACurrent( p->sp( 0 ), nut->spParentNeutrino() );
    tau2 = EvtLeptonVACurrent( p->sp( 1 ), nut->spParentNeutrino() );
    l1   = EvtLeptonVACurrent( nul->spParentNeutrino(), l->spParent( 0 ) );
    l2   = EvtLeptonVACurrent( nul->spParentNeutrino(), l->spParent( 1 ) );
  }
 
  vertex( 0, 0, tau1 * l1 );
  vertex( 0, 1, tau1 * l2 );
  vertex( 1, 0, tau2 * l1 );
  vertex( 1, 1, tau2 * l2 );
 
  return;
}