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/**
* \authors The HEJ collaboration (see AUTHORS for details)
* \date 2019
* \copyright GPLv2 or later
*/
#include "HEJ/PDF.hh"
#include <iostream>
#include <stdexcept>
#include <string>
namespace HEJ{
namespace{
int to_beam(ParticleID id){
if(std::abs(id) == pid::proton){
return (id > 0)?1:-1;
}
throw std::invalid_argument(
"unknown beam type: " + std::to_string(id)
);
}
}
#if defined LHAPDF_MAJOR_VERSION && LHAPDF_MAJOR_VERSION == 6
PDF::PDF(int id, ParticleID beam1, ParticleID beam2):
pdf{LHAPDF::mkPDF(id)},
beamtype{{to_beam(beam1), to_beam(beam2)}}
{}
double PDF::pdfpt(size_t beam_idx, double x, double q, ParticleID id) const{
if(!(inRangeQ(q) && inRangeX(x))) return 0.;
if(id == pid::gluon){
return pdf->xfxQ(21,x,q);
}
else if(abs(id) < 7){
return pdf->xfxQ(id*beamtype[beam_idx],x,q);
}
else {
std::cerr << "particle type unknown: "<< id << std::endl;
return 0.0;
}
}
double PDF::Halphas(double q) const{
double as = pdf->alphasQ(q);
if (std::isnan(as) || as > 0.5) {
as = 0.5;
}
return as;
}
int PDF::id() const{
return pdf->lhapdfID();
};
bool PDF::inRangeQ(double q) const{
return pdf->inRangeQ(q);
}
bool PDF::inRangeX(double x) const{
return pdf->inRangeX(x);
}
#else /* LHAPDF version unknown or older than 6 */
PDF::PDF(std::string LHAPDFName, int LHAPDFsubset, ParticleID beam1, ParticleID beam2):
beamtype{{to_beam(beam1_type), to_beam(beam2_type)}}
{
LHAPDF::initPDFSet(LHAPDFName, LHAPDF::LHGRID, LHAPDFsubset);
}
double PDF::pdfpt(size_t beam_idx, double x, double q, ParticleID id) const{
if(!(inRangeQ(q) && inRangeX(x))) return 0.;
if (id == pid::gluon){
return LHAPDF::xfx(x,q,0);
}
else if (abs(id) < 7){
return LHAPDF::xfx(x,q,id*beamtype[beam_idx]);
}
else {
std::cerr << "particle type unknown: "<< id <<std::endl;
return 0.0;
}
}
double PDF::Halphas(double q) const{
double as = LHAPDF::alphasPDF(q);
if (isnan(as) || as > 0.5) as = 0.5;
return as;
}
bool PDF::inRangeQ(double q) const{
// here we assume that all members actually have the same range!
static constexpr int member = 0;
return (LHAPDF::getQ2min(member) < q*q) && (q*q < LHAPDF::getQ2max(member));
}
bool PDF::inRangeX(double x) const{
// here we assume that all members actually have the same range!
static constexpr int member = 0;
return (LHAPDF::getXmin(member) < x) && (x < LHAPDF::getXmax(member));
}
#endif
}

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