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MEMinBias.cc
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MEMinBias.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the MEMinBias class.
//
#include "MEMinBias.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Utilities/SimplePhaseSpace.h"
//#include "ThePEG/Repository/EventGenerator.h"
#include "ThePEG/Handlers/StandardXComb.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
using namespace Herwig;
#include "ThePEG/PDT/EnumParticles.h"
#include "ThePEG/MatrixElement/Tree2toNDiagram.h"
void MEMinBias::getDiagrams() const {
int maxflav(2);
// Pomeron data
tcPDPtr pom = getParticleData(990);
for ( int i = 1; i <= maxflav; ++i ) {
for( int j=1; j <= i; ++j){
tcPDPtr q1 = getParticleData(i);
tcPDPtr q1b = q1->CC();
tcPDPtr q2 = getParticleData(j);
tcPDPtr q2b = q2->CC();
// For each flavour we add:
//qq -> qq
add(new_ptr((Tree2toNDiagram(3), q1, pom, q2, 1, q1, 2, q2, -1)));
//qqb -> qqb
add(new_ptr((Tree2toNDiagram(3), q1, pom, q2b, 1, q1, 2, q2b, -2)));
//qbqb -> qbqb
add(new_ptr((Tree2toNDiagram(3), q1b, pom, q2b, 1, q1b, 2, q2b, -3)));
}
}
}
Energy2 MEMinBias::scale() const {
return sqr(10*GeV);
}
int MEMinBias::nDim() const {
return 0;
}
void MEMinBias::setKinematics() {
HwMEBase::setKinematics(); // Always call the base class method first.
}
bool MEMinBias::generateKinematics(const double *) {
// generate the masses of the particles
for ( int i = 2, N = meMomenta().size(); i < N; ++i ) {
meMomenta()[i] = Lorentz5Momentum(mePartonData()[i]->generateMass());
}
Energy q = ZERO;
try {
q = SimplePhaseSpace::
getMagnitude(sHat(), meMomenta()[2].mass(), meMomenta()[3].mass());
} catch ( ImpossibleKinematics ) {
return false;
}
Energy pt = ZERO;
meMomenta()[2].setVect(Momentum3( pt, pt, q));
meMomenta()[3].setVect(Momentum3(-pt, -pt, -q));
meMomenta()[2].rescaleEnergy();
meMomenta()[3].rescaleEnergy();
jacobian(1.0);
return true;
}
double MEMinBias::me2() const {
return 1.0;
}
CrossSection MEMinBias::dSigHatDR() const {
return me2()*jacobian()/sHat()*sqr(hbarc);
}
unsigned int MEMinBias::orderInAlphaS() const {
return 0;
}
unsigned int MEMinBias::orderInAlphaEW() const {
return 2;
}
Selector<MEBase::DiagramIndex>
MEMinBias::diagrams(const DiagramVector & diags) const {
Selector<DiagramIndex> sel;
for ( DiagramIndex i = 0; i < diags.size(); ++i )
sel.insert(1.0, i);
return sel;
}
Selector<const ColourLines *>
MEMinBias::colourGeometries(tcDiagPtr diag) const {
static ColourLines qq("1 4, 3 5");
static ColourLines qqb("1 4, -3 -5");
static ColourLines qbqb("-1 -4, -3 -5");
Selector<const ColourLines *> sel;
switch(diag->id()){
case -1:
sel.insert(1.0, &qq);
break;
case -2:
sel.insert(1.0, &qqb);
break;
case -3:
sel.insert(1.0, &qbqb);
break;
}
return sel;
}
IBPtr MEMinBias::clone() const {
return new_ptr(*this);
}
IBPtr MEMinBias::fullclone() const {
return new_ptr(*this);
}
ClassDescription<MEMinBias> MEMinBias::initMEMinBias;
// Definition of the static class description member.
void MEMinBias::Init() {
static ClassDocumentation<MEMinBias> documentation
("There is no documentation for the MEMinBias class");
}

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