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LeptonLeptonPDF.cc
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// -*- C++ -*-
//
// LeptonLeptonPDF.cc is a part of ThePEG - Toolkit for HEP Event Generation
// Copyright (C) 1999-2007 Leif Lonnblad
//
// ThePEG 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 LeptonLeptonPDF class.
//
#include "LeptonLeptonPDF.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Utilities/Maths.h"
#include "ThePEG/PDT/ParticleData.h"
#include "ThePEG/Repository/EventGenerator.h"
#include "ThePEG/StandardModel/StandardModelBase.h"
#include "ThePEG/Interface/ClassDocumentation.h"
using namespace ThePEG;
IBPtr LeptonLeptonPDF::clone() const {
return new_ptr(*this);
}
IBPtr LeptonLeptonPDF::fullclone() const {
return new_ptr(*this);
}
bool LeptonLeptonPDF::canHandleParticle(tcPDPtr particle) const {
return ( abs(particle->id()) < 20 || abs(particle->id()) > 10 );
}
bool LeptonLeptonPDF::hasPoleIn1(tcPDPtr particle, tcPDPtr parton) const {
return particle == parton;
}
cPDVector LeptonLeptonPDF::partons(tcPDPtr p) const {
cPDVector ret;
if ( canHandleParticle(p) ) ret.push_back(p);
return ret;
}
double LeptonLeptonPDF::
xfl(tcPDPtr particle, tcPDPtr parton, Energy2 partonScale, double l,
Energy2) const {
using namespace Constants;
if ( parton != particle || l <= 0.0 ) return 0.0;
static const double gf = 3.0/4.0 - EulerGamma;
const double x = exp(-l);
const double eps = Math::exp1m(-l);
const double lx = -l;
const double l1x = log(eps);
const double beta2 =
SM().alphaEM()*(log(partonScale/sqr(particle->mass()))-1.0)/pi;
return x*(exp(l1x*(beta2 - 1.0) + log(beta2) + gf*beta2)/Math::gamma(beta2+1.0)
- 0.5*beta2*(1.0+x) + sqr(beta2)*((1.0+x)*(-4.0*l1x+3.0*lx)
- 4.0*lx/eps - 5.0 - x)/8.0);
}
double LeptonLeptonPDF::
xfvl(tcPDPtr particle, tcPDPtr parton, Energy2 partonScale,
double l, Energy2 particleScale) const {
return xfl(particle, parton, partonScale, l, particleScale);
}
double LeptonLeptonPDF::
xfvx(tcPDPtr particle, tcPDPtr parton, Energy2 partonScale,
double x, double eps, Energy2 particleScale) const {
using Math::log1m;
return xfl(particle, parton, partonScale,
(x < 0.5 || eps <= 0.0)? -log(x): -log1m(eps), particleScale);
}
double LeptonLeptonPDF::
flattenL(tcPDPtr particle, tcPDPtr,
const PDFCuts & c, double z, double & jacobian) const {
using namespace Constants;
using Math::log1m;
Energy2 scale = min(c.sMax(), c.scaleMax());
if ( c.scaleMin() > 0.0*GeV2 ) scale = min(scale, c.scaleMin());
double beta2 =
SM().alphaEM()*(log(scale/sqr(particle->mass()))-1.0)/pi;
// double zpow = pow(z, 1.0/beta2);
// jacobian = zpow/(1.0/beta2+1);
// return z*zpow;
// double l = pow(z, 1.0/beta2);
// jacobian = l/(z*beta2);
// z = max(z, pow(std::numeric_limits<double>::min()*1.5, beta2));
double eps = pow(z, 1.0/beta2);
double l = -log1m(eps);
jacobian *= eps/(beta2*z*(1.0 - eps));
return l;
}
NoPIOClassDescription<LeptonLeptonPDF> LeptonLeptonPDF::initLeptonLeptonPDF;
void LeptonLeptonPDF::Init() {
static ClassDocumentation<LeptonLeptonPDF> documentation
("Describes the distribution of leptons within leptons, ie. the energy "
"loss of leptons due to radiation of soft photons.");
}

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