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FFVCurrentDecayer.cc
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FFVCurrentDecayer.cc
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// -*- C++ -*-
//
// FFVCurrentDecayer.cc is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2011 The Herwig Collaboration
//
// Herwig++ is licenced under version 2 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
//
// This is the implementation of the non-inlined, non-templated member
// functions of the FFVCurrentDecayer class.
//
#include "FFVCurrentDecayer.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
#include "ThePEG/Helicity/WaveFunction/SpinorWaveFunction.h"
#include "ThePEG/Helicity/WaveFunction/SpinorBarWaveFunction.h"
#include "ThePEG/StandardModel/StandardModelBase.h"
using namespace Herwig;
using ThePEG::Helicity::u_spinortype;
using ThePEG::Helicity::v_spinortype;
using ThePEG::Helicity::VectorWaveFunction;
using ThePEG::Helicity::SpinorWaveFunction;
using ThePEG::Helicity::SpinorBarWaveFunction;
using ThePEG::Helicity::Direction;
using ThePEG::Helicity::incoming;
using ThePEG::Helicity::outgoing;
IBPtr FFVCurrentDecayer::clone() const {
return new_ptr(*this);
}
IBPtr FFVCurrentDecayer::fullclone() const {
return new_ptr(*this);
}
void FFVCurrentDecayer::doinit() {
_theFFVPtr = dynamic_ptr_cast<FFVVertexPtr>(getVertex());
GeneralCurrentDecayer::doinit();
}
void FFVCurrentDecayer::rebind(const TranslationMap & trans)
{
_theFFVPtr = trans.translate(_theFFVPtr);
GeneralCurrentDecayer::rebind(trans);
}
IVector FFVCurrentDecayer::getReferences() {
IVector ret = GeneralCurrentDecayer::getReferences();
ret.push_back(_theFFVPtr);
return ret;
}
void FFVCurrentDecayer::persistentOutput(PersistentOStream & os) const {
os << _theFFVPtr;
}
void FFVCurrentDecayer::persistentInput(PersistentIStream & is, int) {
is >> _theFFVPtr;
}
ClassDescription<FFVCurrentDecayer> FFVCurrentDecayer::initFFVCurrentDecayer;
// Definition of the static class description member.
void FFVCurrentDecayer::Init() {
static ClassDocumentation<FFVCurrentDecayer> documentation
("There is no documentation for the FFVCurrentDecayer class");
}
double FFVCurrentDecayer::me2(const int ichan, const Particle & inpart,
const ParticleVector & decay,
MEOption meopt) const {
// get the particles for the hadronic curret
Energy q;
ParticleVector hadpart(decay.begin()+1,decay.end());
// fermion types
int itype[2];
if(inpart.dataPtr()->CC()) itype[0] = inpart.id() > 0 ? 0 : 1;
else itype[0] = 2;
if(decay[0]->dataPtr()->CC()) itype[1] = decay[0]->id() > 0 ? 0 : 1;
else itype[1] = 2;
//Need to use different barred or unbarred spinors depending on
//whether particle is cc or not.
bool ferm(itype[0] == 0 || itype[1] == 0 || (itype[0] == 2 && itype[1] == 2));
if(meopt==Initialize) {
// spinors and rho
if(ferm) {
SpinorWaveFunction ::calculateWaveFunctions(_wave,_rho,
const_ptr_cast<tPPtr>(&inpart),
incoming);
if(_wave[0].wave().Type() != u_spinortype)
for(unsigned int ix = 0; ix < 2; ++ix) _wave [ix].conjugate();
}
else {
SpinorBarWaveFunction::calculateWaveFunctions(_wavebar,_rho,
const_ptr_cast<tPPtr>(&inpart),
incoming);
if(_wavebar[0].wave().Type() != v_spinortype)
for(unsigned int ix = 0; ix < 2; ++ix) _wavebar[ix].conjugate();
}
}
// setup spin info when needed
if(meopt==Terminate) {
// for the decaying particle
if(ferm) {
SpinorWaveFunction::
constructSpinInfo(_wave,const_ptr_cast<tPPtr>(&inpart),incoming,true);
SpinorBarWaveFunction::constructSpinInfo(_wavebar,decay[0],outgoing,true);
}
else {
SpinorBarWaveFunction::
constructSpinInfo(_wavebar,const_ptr_cast<tPPtr>(&inpart),incoming,true);
SpinorWaveFunction::constructSpinInfo(_wave,decay[0],outgoing,true);
}
weakCurrent()->current(mode(),ichan,q,hadpart,meopt);
return 0.;
}
Energy2 scale(sqr(inpart.mass()));
if(ferm)
SpinorBarWaveFunction::
calculateWaveFunctions(_wavebar,decay[0],outgoing);
else
SpinorWaveFunction::
calculateWaveFunctions(_wave ,decay[0],outgoing);
// calculate the hadron current
vector<LorentzPolarizationVectorE>
hadron(weakCurrent()->current(mode(),ichan,q,hadpart,meopt));
// prefactor
double pre = sqr(pow(inpart.mass()/q,int(hadpart.size()-2)));
// work out the mapping for the hadron vector
vector<unsigned int> constants(decay.size()+1),ihel(decay.size()+1);
vector<PDT::Spin> ispin(decay.size());
int itemp(1);
unsigned int hhel,ix(decay.size());
do {
--ix;
ispin[ix]=decay[ix]->data().iSpin();
itemp*=ispin[ix];
constants[ix]=itemp;
}
while(ix>0);
constants[decay.size()]=1;
constants[0]=constants[1];
// compute the matrix element
DecayMatrixElement newME(PDT::Spin1Half,ispin);
VectorWaveFunction vWave;
tcPDPtr vec= inpart.dataPtr()->iCharge()-decay[0]->dataPtr()->iCharge() > 0
? getParticleData(ParticleID::Wplus) : getParticleData(ParticleID::Wminus);
Lorentz5Momentum vmom=inpart.momentum()-decay[0]->momentum();
vmom.rescaleMass();
for(hhel=0;hhel<hadron.size();++hhel) {
// map the index for the hadrons to a helicity state
for(ix=decay.size();ix>1;--ix) ihel[ix]=(hhel%constants[ix-1])/constants[ix];
vWave=VectorWaveFunction(vmom,vec,hadron[hhel]*UnitRemoval::InvE,outgoing);
for(unsigned int if1 = 0; if1 < 2; ++if1) {
for(unsigned int if2 = 0; if2 < 2; ++if2) {
ihel[0]=if1;
ihel[1]=if2;
if(!ferm) swap(ihel[0],ihel[1]);
newME(ihel) = _theFFVPtr->evaluate(scale,_wave[if1],_wavebar[if2],vWave);
}
}
}
// store the matrix element
ME(newME);
// multiply by the CKM element
int iq,ia;
weakCurrent()->decayModeInfo(mode(),iq,ia);
double ckm(1.);
if(iq<=6) {
if(iq%2==0) ckm = SM().CKM(iq/2-1,(abs(ia)-1)/2);
else ckm = SM().CKM(abs(ia)/2-1,(iq-1)/2);
}
pre /= 0.125*sqr(_theFFVPtr->weakCoupling(scale));
double output(0.5*pre*ckm*(ME().contract(_rho)).real()*
sqr(SM().fermiConstant()*UnitRemoval::E2));
return output;
}
Energy FFVCurrentDecayer::partialWidth(tPDPtr inpart, tPDPtr outa,
vector<tPDPtr> currout) {
vector<long> id;
id.push_back(inpart->id());
id.push_back(outa->id());
for(unsigned int ix=0;ix<currout.size();++ix) id.push_back(currout[ix]->id());
bool cc;
int mode=modeNumber(cc,id);
imode(mode);
return initializePhaseSpaceMode(mode,true,true);
}

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