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SMHPPVertex.cc
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SMHPPVertex.cc
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// -*- C++ -*-
//
// SMHPPVertex.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 SMHPPVertex class.
//
#include "SMHPPVertex.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/Switch.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/PDT/EnumParticles.h"
#include "Herwig++/Looptools/clooptools.h"
using namespace Herwig;
using namespace ThePEG;
void SMHPPVertex::persistentOutput(PersistentOStream & os) const {
os << _theSM << ounit(_mw,GeV) << massopt << _minloop << _maxloop
<< _CoefRepresentation;
}
void SMHPPVertex::persistentInput(PersistentIStream & is, int) {
is >> _theSM >> iunit(_mw, GeV) >> massopt >> _minloop >> _maxloop
>> _CoefRepresentation;
}
ClassDescription<SMHPPVertex> SMHPPVertex::initSMHPPVertex;
// Definition of the static class description member.
void SMHPPVertex::Init() {
static ClassDocumentation<SMHPPVertex> documentation
("This class implements the h0->gamma,gamma vertex.");
static Parameter<SMHPPVertex,int> interfaceMinQuarkInLoop
("MinQuarkInLoop",
"The minimum flavour of the quarks to include in the loops",
&SMHPPVertex::_minloop, 6, 1, 6,
false, false, Interface::limited);
static Parameter<SMHPPVertex,int> interfaceMaxQuarkInLoop
("MaxQuarkInLoop",
"The maximum flavour of the quarks to include in the loops",
&SMHPPVertex::_maxloop, 6, 1, 6,
false, false, Interface::limited);
static Switch<SMHPPVertex,unsigned int> interfaceMassOption
("LoopMassScheme",
"Switch for the treatment of the masses in the loops ",
&SMHPPVertex::massopt, 2, false, false);
static SwitchOption interfaceHeavyMass
(interfaceMassOption,
"PoleMasses",
"The loop is calculcated with the pole quark masses",
1);
static SwitchOption interfaceNormalMass
(interfaceMassOption,
"RunningMasses",
"running quark masses are taken in the loop",
2);
static Switch<SMHPPVertex,unsigned int> interfaceScheme
("CoefficientScheme",
"Which scheme for the tensor coefficients is applied",
&SMHPPVertex::_CoefRepresentation, 1, false, false);
static SwitchOption interfaceSchemeSimplified
(interfaceScheme,
"Simplified",
"Represection suitable for the simplified the H-g-g and H-gamma-gamma vertices",
1);
static SwitchOption interfaceSchemeGeneral
(interfaceScheme,
"General",
"Represection suitable for the Passarino-Veltman tensor reduction scheme",
2);
}
void SMHPPVertex::setCoupling(Energy2 q2, tcPDPtr part2,
tcPDPtr part3, tcPDPtr part1) {
assert( part1->id() == ParticleID::h0 &&
part2->id() == ParticleID::gamma && part3->id() == ParticleID::gamma );
int Qminloop = _minloop;
int Qmaxloop = _maxloop;
if (_maxloop < _minloop) {
Qmaxloop=_minloop;
Qminloop=_maxloop;
}
switch (_CoefRepresentation) {
case 1: {
if(q2 != _q2last||_couplast==0.) {
double g = weakCoupling(q2);
double e2 = sqr(electroMagneticCoupling(q2));
_couplast = UnitRemoval::E * e2 * g / 8. / _mw/ sqr(Constants::pi);
_q2last = q2;
}
norm(_couplast);
Complex loop(0.);
// quark loops
for ( int i = Qminloop; i <= Qmaxloop; ++i ) {
tcPDPtr qrk = getParticleData(i);
Energy mass = (2 == massopt) ? _theSM->mass(q2,qrk) : qrk->mass();
Charge charge = qrk->charge();
loop += 3.*sqr(charge/ThePEG::Units::eplus) * Af(sqr(mass)/q2);
}
// lepton loops
int Lminloop = 3; // still fixed value
int Lmaxloop = 3; // still fixed value
for (int i = Lminloop; i <= Lmaxloop; ++i) {
tcPDPtr lpt = getParticleData(9 + 2*i);
Energy mass = (2 == massopt) ? _theSM->mass(q2,lpt) : lpt->mass();
Charge charge = lpt->charge();
loop += sqr(charge/ThePEG::Units::eplus) * Af(sqr(mass)/q2);
}
// W loop
loop += Aw(sqr(_mw)/q2);
a00(loop);
a11(0.0);
a12(0.0);
a21(-loop);
a22(0.0);
aEp(0.0);
break;
}
case 2: {
if(q2 != _q2last||_couplast==0.) {
clearcache();
double e = electroMagneticCoupling(q2);
_couplast = pow(e,3)/sqrt(sin2ThetaW());
_q2last = q2;
}
norm(_couplast);
// quarks
int delta = Qmaxloop - Qminloop + 1;
type.resize(delta,PDT::SpinUnknown);
masses.resize(delta,ZERO);
for (int i = 0; i < delta; ++i) {
tcPDPtr q = getParticleData(_minloop+i);
type[i] = PDT::Spin1Half;
masses[i] = (2 == massopt) ? _theSM->mass(q2,q) : q->mass();
double copl = -masses[i]*3.*sqr(q->iCharge()/3.)/_mw/2.;
couplings.push_back(make_pair(copl, copl));
}
// tau
type.push_back(PDT::Spin1Half);
tcPDPtr tau = getParticleData(ParticleID::tauminus);
masses.push_back(_theSM->mass(q2,tau));
double copl = -masses.back()*sqr(tau->iCharge()/3.)/_mw/2.;
couplings.push_back(make_pair(copl, copl));
// W
type.push_back(PDT::Spin1);
masses.push_back(_mw);
couplings.push_back(make_pair(UnitRemoval::InvE*_mw, UnitRemoval::InvE*_mw));
setNParticles(delta+2);
VVSLoopVertex::setCoupling(q2, part1, part2, part3);
break;
}
}
}
Complex SMHPPVertex::Af(const double tau) const {
return tau*(4. - W2(tau)*(1. - 4.*tau));
}
Complex SMHPPVertex::Aw(const double tau) const {
return 0.5*(-3.*W2(tau)*tau*(4.*tau - 2.) - 12.*tau - 2.);
}
Complex SMHPPVertex::W2(double lambda) const {
double pi = Constants::pi;
if (0.0 == lambda)
return 0.0;
if (lambda < 0.0)
return 4.*sqr(asinh(0.5*sqrt(-1./lambda)));
double root(0.5*sqrt(1./lambda));
Complex ac(0.);
// formulae from NPB297,221
if(root < 1.) {
ac = -sqr(asin(root));
}
else {
double ex = acosh(root);
ac = sqr(ex) - 0.25*sqr(pi) - pi*ex*Complex(0.,1.);
}
return 4.*ac;
}
SMHPPVertex::SMHPPVertex()
:_couplast(0.),_q2last(),_mw(),massopt(1),
_minloop(6),_maxloop(6),_CoefRepresentation(1) {
//PDG codes for particles at vertices
addToList(22,22,25);
}
// functions for loops for testing
// namespace {
// Complex F0(double tau) {
// Complex ft;
// if(tau>=1.)
// ft = sqr(asin(1./sqrt(tau)));
// else {
// double etap = 1.+sqrt(1.-tau);
// double etam = 1.-sqrt(1.-tau);
// ft = -0.25*sqr(log(etap/etam)-Constants::pi*Complex(0.,1.));
// }
// return tau*(1.-tau*ft);
// }
// Complex FHalf(double tau,double eta) {
// Complex ft;
// if(tau>=1.)
// ft = sqr(asin(1./sqrt(tau)));
// else {
// double etap = 1.+sqrt(1.-tau);
// double etam = 1.-sqrt(1.-tau);
// ft = -0.25*sqr(log(etap/etam)-Constants::pi*Complex(0.,1.));
// }
// return -2.*tau*(eta+(1.-tau*eta)*ft);
// }
// Complex F1(double tau) {
// Complex ft;
// if(tau>=1.)
// ft = sqr(asin(1./sqrt(tau)));
// else {
// double etap = 1.+sqrt(1.-tau);
// double etam = 1.-sqrt(1.-tau);
// ft = -0.25*sqr(log(etap/etam)-Constants::pi*Complex(0.,1.));
// }
// return 2.+3.*tau+3.*tau*(2.-tau)*ft;
// }
// }
void SMHPPVertex::doinit() {
_theSM = dynamic_ptr_cast<tcHwSMPtr>(generator()->standardModel());
if( !_theSM )
throw InitException()
<< "SMHGGVertex::doinit() - The pointer to the SM object is null."
<< Exception::abortnow;
_mw = getParticleData(ThePEG::ParticleID::Wplus)->mass();
orderInGs(0);
orderInGem(3);
VVSLoopVertex::doinit();
// // code to test the partial width
// Energy mh = getParticleData(25)->mass();
// Complex I(0.);
// for(long ix=int(_minloop);ix<=int(_maxloop);++ix) {
// tcPDPtr qrk = getParticleData(ix);
// Energy mt = (2 == massopt) ? _theSM->mass(sqr(mh),qrk) : qrk->mass();
// double tau = sqr(2.*mt/mh);
// I += 3.*sqr(double(qrk->iCharge())/3.)*FHalf(tau,1.);
// cerr << "testing half " << FHalf(tau,1) << " " << Af(0.25*tau) << "\n";
// }
// for(long ix=15;ix<=15;++ix) {
// tcPDPtr qrk = getParticleData(ix);
// Energy mt = (2 == massopt) ? _theSM->mass(sqr(mh),qrk) : qrk->mass();
// double tau = sqr(2.*mt/mh);
// I += sqr(double(qrk->iCharge())/3.)*FHalf(tau,1.);
// }
// I += F1(sqr(2.*_mw/mh));
// Energy width = sqr(weakCoupling(sqr(mh))*sqr(electroMagneticCoupling(sqr(mh))))
// /1024./pow(Constants::pi,5)/16.*sqr(mh/_mw)*mh*std::norm(I);
// cerr << "testing anal " << width/GeV << "\n";
}

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