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MEff2ss.cc
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// -*- C++ -*-
//
// MEff2ss.cc is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2007 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 MEff2ss class.
//
#include "MEff2ss.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Handlers/StandardXComb.h"
#include "ThePEG/Helicity/WaveFunction/VectorWaveFunction.h"
#include "ThePEG/Helicity/WaveFunction/TensorWaveFunction.h"
#include "ThePEG/StandardModel/StandardModelBase.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "HardVertex.h"
#include <numeric>
using namespace Herwig;
using ThePEG::Helicity::VectorWaveFunction;
using ThePEG::Helicity::TensorWaveFunction;
using ThePEG::Helicity::incoming;
using ThePEG::Helicity::outgoing;
void MEff2ss::doinit() throw(InitException) {
GeneralHardME::doinit();
HPCount ndiags(numberOfDiags());
theFerm.resize(ndiags);
theVec.resize(ndiags);
theTen.resize(ndiags);
for(HPCount i = 0; i < ndiags; ++i) {
HPDiagram current = getProcessInfo()[i];
if(current.channelType == HPDiagram::tChannel) {
if(current.intermediate->iSpin() == PDT::Spin1Half)
theFerm[i] =
make_pair(dynamic_ptr_cast<AbstractFFSVertexPtr>(current.vertices.first),
dynamic_ptr_cast<AbstractFFSVertexPtr>(current.vertices.second));
}
else if(current.channelType == HPDiagram::sChannel) {
if(current.intermediate->iSpin() == PDT::Spin1)
theVec[i] =
make_pair(dynamic_ptr_cast<AbstractFFVVertexPtr>(current.vertices.first),
dynamic_ptr_cast<AbstractVSSVertexPtr>(current.vertices.second));
if(current.intermediate->iSpin() == PDT::Spin2)
theTen[i] =
make_pair(dynamic_ptr_cast<AbstractFFTVertexPtr>(current.vertices.first),
dynamic_ptr_cast<AbstractSSTVertexPtr>(current.vertices.second));
}
else
throw InitException() << "MEFF2ss:doinit() - Cannot find correct "
<< "channel from diagram. Vertex not cast! "
<< Exception::runerror;
}
}
double MEff2ss::me2() const {
//first setup wavefunctions for external particles
SpinorVector sp(2);
SpinorBarVector sbar(2);
for( unsigned int i = 0; i < 2; ++i ) {
sp[i] = SpinorWaveFunction(meMomenta()[0], mePartonData()[0], i,
incoming);
sbar[i] = SpinorBarWaveFunction(meMomenta()[1], mePartonData()[1], i,
incoming);
}
ScalarWaveFunction sca1(meMomenta()[2], mePartonData()[2],
Complex(1.), outgoing);
ScalarWaveFunction sca2(meMomenta()[3], mePartonData()[3],
Complex(1.), outgoing);
double full_me(0.);
ff2ssME(sp, sbar, sca1, sca2, full_me);
#ifndef NDEBUG
if( debugME() ) debug(full_me);
#endif
return full_me;
}
ProductionMatrixElement
MEff2ss::ff2ssME(const SpinorVector & sp, const SpinorBarVector & sbar,
const ScalarWaveFunction & sca1,
const ScalarWaveFunction & sca2, double & me2) const {
//Define factors
const Energy2 q2(scale());
const vector<vector<double> > cfactors = getColourFactors();
const HPCount ndiags = numberOfDiags();
const size_t ncf = numberOfFlows();
vector<double> me(ndiags, 0.);
vector<Complex> diag(ndiags, Complex(0.)), flows(ncf, Complex(0.));
ScalarWaveFunction interS; VectorWaveFunction interV;
SpinorBarWaveFunction interFB; TensorWaveFunction interT;
ProductionMatrixElement pme(PDT::Spin1Half, PDT::Spin1Half,
PDT::Spin0, PDT::Spin0);
for(unsigned int if1 = 0; if1 < 2; ++if1) {
for(unsigned int if2 = 0; if2 < 2; ++if2) {
flows = vector<Complex>(ncf, Complex(0.));
for(HPCount ix = 0; ix < ndiags; ++ix) {
HPDiagram current = getProcessInfo()[ix];
tcPDPtr internal(current.intermediate);
if(current.channelType == HPDiagram::tChannel &&
internal->iSpin() == PDT::Spin1Half) {
if(current.ordered.second) {
interFB = theFerm[ix].second->evaluate(q2, 3, internal, sbar[if2],
sca2);
diag[ix] = theFerm[ix].first->evaluate(q2, sp[if1], interFB, sca1);
}
else {
interFB = theFerm[ix].second->evaluate(q2, 3, internal, sbar[if2],
sca1);
diag[ix] = theFerm[ix].first->evaluate(q2, sp[if1], interFB, sca2);
}
}
else if(current.channelType == HPDiagram::sChannel) {
if(internal->iSpin() == PDT::Spin1) {
interV = theVec[ix].first->evaluate(q2, 1, internal, sp[if1],
sbar[if2]);
diag[ix] = theVec[ix].second->evaluate(q2, interV, sca2, sca1);
}
else if(internal->iSpin() == PDT::Spin2) {
interT = theTen[ix].first->evaluate(q2, 1, internal, sp[if1],
sbar[if2]);
diag[ix] = theTen[ix].second ->evaluate(q2, sca2, sca1, interT);
}
else
diag[ix] = 0.;
}
me[ix] += norm(diag[ix]);
//colourflows
for(unsigned int iy = 0; iy < current.colourFlow.size(); ++iy)
flows[current.colourFlow[iy].first - 1] +=
current.colourFlow[iy].second * diag[ix];
}//end of diag loop
//set the appropriate element of the ProductionMatrixElement
pme(if1, if2, 0, 0) =
std::accumulate(flows.begin(), flows.end(), Complex(0.0,0.0));
for(unsigned int ii = 0; ii < ncf; ++ii)
for(unsigned int ij = 0; ij < ncf; ++ij)
me2 += cfactors[ii][ij]*(flows[ii]*conj(flows[ij])).real();
}
}
const double identFact = mePartonData()[2]->id() == mePartonData()[3]->id()
? 0.5 : 1;
int cola = mePartonData()[0]->iColour();
const double colourAvg = ( abs(cola) == 3 ) ? 1./9. : 1.;
DVector save(ndiags);
for(DVector::size_type ix = 0; ix < ndiags; ++ix)
save[ix] = 0.25*identFact*colourAvg*me[ix];
meInfo(save);
me2 *= 0.25*identFact*colourAvg;
return pme;
}
Selector<const ColourLines *>
MEff2ss::colourGeometries(tcDiagPtr diag) const {
static vector<ColourLines> cf(16);
//33b->33b
cf[0] = ColourLines("1 2 -3, 4 -2 -5");
cf[1] = ColourLines("1 3 4, -2 -3 -5");
cf[2] = ColourLines("1 4, -3 -5");
cf[3] = ColourLines("1 -2, 4 -5");
//33->33
cf[4] = ColourLines("1 2 5, 3 -2 4");
cf[5] = ColourLines("1 2 4, 3 -2 5");
cf[6] = ColourLines("1 4, 3 5");
cf[7] = ColourLines("1 5, 3 4");
//3b3b->3b3b
cf[8] = ColourLines("-1 -2 -5, -3 2 -4");
cf[9] = ColourLines("-1 -2 -4, -3 2 -5");
cf[10] = ColourLines("-1 -4, -3 -5");
cf[11] = ColourLines("-1 -5, -3 -4");
//33b->11
cf[12] = ColourLines("1 2 -3");
cf[13] = ColourLines("1 -2");
//11->11
cf[14] = ColourLines("");
//11->33b
cf[15] = ColourLines("4 -5");
HPDiagram current = getProcessInfo()[abs(diag->id()) - 1];
vector<ColourLines>::size_type cl(0);
PDT::Colour inac(mePartonData()[0]->iColour());
PDT::Colour inbc(mePartonData()[1]->iColour());
PDT::Colour outac(mePartonData()[2]->iColour());
if(inac == PDT::Colour0 && inbc == PDT::Colour0) {
cl = outac == PDT::Colour0 ? 14 : 15;
}
else if(inac == PDT::Colour3 && inbc == PDT::Colour3) {
if(current.intermediate->iColour() == PDT::Colour8)
cl = current.ordered.second ? 4 : 5;
else
cl = current.ordered.second ? 6 : 7;
}
else if(inac == PDT::Colour3bar && inbc == PDT::Colour3bar) {
if(current.intermediate->iColour() == PDT::Colour8)
cl = current.ordered.second ? 8 : 9;
else
cl = current.ordered.second ? 10 : 11 ;
}
else {
if(outac == PDT::Colour3) {
if(current.intermediate->iColour() == PDT::Colour8)
cl = current.channelType == HPDiagram::tChannel ? 0 : 1;
else
cl = current.channelType == HPDiagram::tChannel ? 2 : 3;
}
else
cl = current.channelType == HPDiagram::tChannel ? 12 : 13;
}
Selector<const ColourLines *> sel;
sel.insert(1., &cf[cl]);
return sel;
}
void MEff2ss::persistentOutput(PersistentOStream & os) const {
os << theFerm << theVec << theTen;
}
void MEff2ss::persistentInput(PersistentIStream & is, int) {
is >> theFerm >> theVec >> theTen;
}
ClassDescription<MEff2ss> MEff2ss::initMEff2ss;
// Definition of the static class description member.
void MEff2ss::Init() {
static ClassDocumentation<MEff2ss> documentation
("MEff2ss implements the ME calculation of the fermion-antifermion "
"to scalar-scalar hard process.");
}
void MEff2ss::constructVertex(tSubProPtr sub) {
//get particles
ParticleVector ext(4);
ext[0] = sub->incoming().first;
ext[1] = sub->incoming().second;
ext[2] = sub->outgoing()[0];
ext[3] = sub->outgoing()[1];
if( ext[0]->id() != mePartonData()[0]->id() ) swap(ext[0], ext[1]);
if( ext[2]->id() != mePartonData()[2]->id() ) swap(ext[2], ext[3]);
SpinorVector sp;
SpinorWaveFunction(sp, ext[0], incoming, false, true);
SpinorBarVector sbar;
SpinorBarWaveFunction(sbar, ext[1], incoming, false, true);
ScalarWaveFunction sca1(ext[2], outgoing, true, true);
ScalarWaveFunction sca2(ext[3], outgoing, true, true);
double dummy(0.);
ProductionMatrixElement pme = ff2ssME(sp, sbar, sca1, sca2, dummy);
#ifndef NDEBUG
if( debugME() ) debug(dummy);
#endif
HardVertexPtr hv = new_ptr(HardVertex());
hv->ME(pme);
for(unsigned int i = 0; i < 4; ++i )
dynamic_ptr_cast<SpinfoPtr>(ext[i]->spinInfo())->setProductionVertex(hv);
}
void MEff2ss::debug(double me2) const {
if( !generator()->logfile().is_open() ) return;
long id1 = mePartonData()[0]->id();
long id2 = mePartonData()[1]->id();
long id3 = mePartonData()[2]->id();
long id4 = mePartonData()[3]->id();
if( (abs(id1) != 1 && abs(id1) != 2) || (abs(id2) != 1 && abs(id2) != 2) ||
( abs(id3) != 1000001 && abs(id3) != 1000002 &&
abs(id3) != 2000001 && abs(id3) != 2000002 ) ||
( abs(id4) != 1000001 && abs(id4) != 1000002 &&
abs(id4) != 2000001 && abs(id4) != 2000002 ) ) return;
tcSMPtr sm = generator()->standardModel();
double gs4 = sqr( 4.*Constants::pi*sm->alphaS(scale()) );
int Nc = sm->Nc();
double Cf = (sqr(Nc) - 1)/2./Nc;
Energy2 s(sHat());
Energy2 mgos = sqr( getParticleData(ParticleID::SUSY_g)->mass());
Energy2 m3s = sqr(mePartonData()[2]->mass());
Energy2 m4s = sqr(mePartonData()[3]->mass());
Energy4 spt2 = uHat()*tHat() - m3s*m4s;
Energy2 tgl(tHat() - mgos), ugl(uHat() - mgos);
unsigned int alpha = abs(id3)/1000000;
unsigned int beta = abs(id4)/1000000;
bool iflav = ( abs(id1) == abs(id2) );
unsigned int oflav = ( abs(id3) - abs(id1) ) % 10;
double analytic(0.);
if( alpha != beta ) {
if( ( id1 > 0 && id2 > 0) ||
( id1 < 0 && id2 < 0) ) {
analytic = spt2/sqr(tgl);
if( iflav ) analytic += spt2/sqr(ugl);
}
else {
analytic = s*mgos/sqr(tgl);
}
}
else {
if( oflav != 0 ) {
analytic = 2.*spt2/sqr(s);
}
else if( ( id1 > 0 && id2 > 0) ||
( id1 < 0 && id2 < 0) ) {
analytic = s*mgos/sqr(tgl);
if( iflav ) {
analytic += s*mgos/sqr(ugl) - 2.*s*mgos/Nc/tgl/ugl;
}
analytic /= ( iflav ? 2. : 1.);
}
else {
analytic = spt2/sqr(tgl);
if( iflav ) {
analytic += 2.*spt2/sqr(s) - 2.*spt2/Nc/s/tgl;
}
}
}
analytic *= gs4*Cf/2./Nc;
double diff = abs(analytic - me2);
if( diff > 1e-4 ) {
generator()->log()
<< mePartonData()[0]->PDGName() << ","
<< mePartonData()[1]->PDGName() << "->"
<< mePartonData()[2]->PDGName() << ","
<< mePartonData()[3]->PDGName() << " difference: "
<< setprecision(10) << diff << " ratio: " << analytic/me2
<< '\n';
}
}

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