EvtTauVectornu.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: EvtTauVectornu.cc
//
// Description: The vector decay of the tau meson.
//              E.g., tau- -> rho- + nut
//
// Modification history:
//
//    RYD/SHY   April 23, 1997           Module created
//
//------------------------------------------------------------------------
//
#include "EvtTauVectornu.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>
 
EvtTauVectornu::~EvtTauVectornu() {}
 
void EvtTauVectornu::getName( std::string& model_name ) { model_name = "TAUVECTORNU"; }
 
EvtDecayBase* EvtTauVectornu::clone() { return new EvtTauVectornu; }
 
void EvtTauVectornu::init() {
 
  // check that there are 0 arguments
  checkNArg( 0 );
  checkNDaug( 2 );
 
  checkSpinParent( EvtSpinType::DIRAC );
 
  checkSpinDaughter( 0, EvtSpinType::VECTOR );
  checkSpinDaughter( 1, EvtSpinType::NEUTRINO );
}
 
void EvtTauVectornu::initProbMax() { setProbMax( 55.0 ); }
 
void EvtTauVectornu::decay( EvtParticle* p ) {
 
  static EvtId TAUM = EvtPDL::getId( "tau-" );
  p->initializePhaseSpace( getNDaug(), getDaugs() );
 
  EvtParticle *v, *nut;
  v                = p->getDaug( 0 );
  nut              = p->getDaug( 1 );
  double      mvec = v->mass();
  EvtVector4C tau1, tau2;
 
  if ( p->getId() == TAUM )
  {
    tau1 = EvtLeptonVACurrent( nut->spParentNeutrino(), p->sp( 0 ) );
    tau2 = EvtLeptonVACurrent( nut->spParentNeutrino(), p->sp( 1 ) );
  }
  else
  {
    tau1 = EvtLeptonVACurrent( p->sp( 0 ), nut->spParentNeutrino() );
    tau2 = EvtLeptonVACurrent( p->sp( 1 ), nut->spParentNeutrino() );
  }
 
  double norm = mvec * sqrt( mvec );
 
  vertex( 0, 0, norm * tau1 * ( v->epsParent( 0 ).conj() ) );
  vertex( 0, 1, norm * tau1 * ( v->epsParent( 1 ).conj() ) );
  vertex( 0, 2, norm * tau1 * ( v->epsParent( 2 ).conj() ) );
  vertex( 1, 0, norm * tau2 * ( v->epsParent( 0 ).conj() ) );
  vertex( 1, 1, norm * tau2 * ( v->epsParent( 1 ).conj() ) );
  vertex( 1, 2, norm * tau2 * ( v->epsParent( 2 ).conj() ) );
 
  return;
}