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// -*- C++ -*-
//
// SatPDF.cc is a part of Herwig - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2017 The Herwig Collaboration
//
// Herwig is licenced under version 3 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 SatPDF class.
//
#include "SatPDF.h"
#include "ThePEG/Utilities/DescribeClass.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#ifdef ThePEG_TEMPLATES_IN_CC_FILE
// #include "SatPDF.tcc"
#endif
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/Reference.h"
#include "ThePEG/PDT/ParticleData.h"
#include "ThePEG/PDT/EnumParticles.h"
#include <cassert>
using namespace Herwig;
using namespace ThePEG;
SatPDF::~SatPDF() {}
bool SatPDF::canHandleParticle(tcPDPtr particle) const {
assert(thePDF);
return thePDF->canHandleParticle(particle);
}
cPDVector SatPDF::partons(tcPDPtr particle) const {
assert(thePDF);
return thePDF->partons(particle);
}
double SatPDF::xfx(tcPDPtr particle, tcPDPtr parton, Energy2 partonScale,
double x, double eps, Energy2 particleScale) const {
assert(thePDF);
double xUsed(x);
if( x < theX0 )
xUsed = theX0;
double pdf(thePDF->xfx(particle, parton, partonScale,
xUsed, eps, particleScale));
if( x < theX0 )
pdf *= pow(x/theX0, theExp);
return pdf;
}
double SatPDF::xfvx(tcPDPtr particle, tcPDPtr parton, Energy2 partonScale,
double x, double eps, Energy2 particleScale) const {
// Here we should return the actual valence density.
assert(thePDF);
double xUsed(x);
if( x < theX0 )
xUsed = theX0;
double pdf(thePDF->xfvx(particle, parton, partonScale,
xUsed, eps, particleScale));
if( x < theX0 )
pdf *= pow(x/theX0, theExp);
return pdf;
}
void SatPDF::persistentOutput(PersistentOStream & os) const {
os << thePDF << theX0 << theExp;
}
void SatPDF::persistentInput(PersistentIStream & is, int) {
is >> thePDF >> theX0 >> theExp;
}
// The following static variable is needed for the type
// description system in ThePEG.
DescribeClass<SatPDF,PDFBase>
describeHerwigSatPDF("Herwig::SatPDF", "HwSatPDF.so");
void SatPDF::Init() {
static ClassDocumentation<SatPDF> documentation
("SatPDF is used to modify any given parton density for small values of x. That can be used to mimic saturation effects.");
static Reference<SatPDF,PDFBase> interfacePDF
("PDF",
"pointer to the pdf, which will be modified",
&SatPDF::thePDF, false, false, true, false);
static Parameter<SatPDF,double> interfaceX0
("X0",
"For x values below this one the parametrisation: f(x) = f(x0) * (x/x0)**exp is used",
&SatPDF::theX0, 1.E-4, 0.0, 1.0,
true, false, Interface::limited);
static Parameter<SatPDF,double> interfaceExp
("Exp",
"For x values below X0 the parametrisation: f(x) = f(x0) * (x/x0)**exp is used",
&SatPDF::theExp, 0.0, -10.0, 10.0,
true, false, Interface::limited);
}

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