/usr/include/Pythia8/Pythia8/PartonDistributions.h is in libpythia8-dev 8.1.86-1.
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// Copyright (C) 2014 Torbjorn Sjostrand.
// PYTHIA is licenced under the GNU GPL version 2, see COPYING for details.
// Please respect the MCnet Guidelines, see GUIDELINES for details.
// Header file for parton densities.
// PDF: base class.
// LHAPDF: derived class for interface to the LHAPDF library.
// GRV94L: derived class for the GRV 94L parton densities.
// CTEQ5L: derived class for the CTEQ 5L parton densities.
// MSTWpdf: derived class for MRST LO*, LO**, MSTW 2008 LO, NLO.
// CTEQ6pdf: derived class for CTEQ 6L, 6L1, 66, CT09 MC1, MC2, (MCS?).
// ProtonPoint: unresolved proton with equivalent photon spectrum.
// GRVpiL: derived class for the GRV LO pion parton densities.
// PomFix: derived class for Q2-independent Pomeron parton densities.
// PomH1FitAB: derived class for the H1 2006 Fit A and Fit B Pomeron PDFs.
// PomH1Jets: derived class for the H1 2007 Jets Pomeron PDFs.
// Lepton: derived class for parton densities inside a lepton.
// LeptonPoint: derived class for unresolved lepton (mainly dummy).
// NNPDF: derived class for the NNPDF2.3 QCD+QED PDF sets.
#ifndef Pythia8_PartonDistributions_H
#define Pythia8_PartonDistributions_H
#include "Pythia8/Basics.h"
#include "Pythia8/Info.h"
#include "Pythia8/ParticleData.h"
#include "Pythia8/PythiaStdlib.h"
namespace Pythia8 {
//==========================================================================
// Base class for parton distribution functions.
class PDF {
public:
// Constructor.
PDF(int idBeamIn = 2212) {idBeam = idBeamIn; idBeamAbs = abs(idBeam);
setValenceContent(); idSav = 9; xSav = -1.; Q2Sav = -1.;
xu = 0.; xd = 0.; xs = 0.; xubar = 0.; xdbar = 0.; xsbar = 0.; xc = 0.;
xb = 0.; xg = 0.; xlepton = 0.; xgamma = 0.; xuVal = 0.; xuSea = 0.;
xdVal = 0.; xdSea = 0.; isSet = true; isInit = false;}
// Destructor.
virtual ~PDF() {}
// Confirm that PDF has been set up (important for LHAPDF and H1 Pomeron).
bool isSetup() {return isSet;}
// Dynamic choice of meson valence flavours for pi0, K0S, K0L, Pomeron.
void newValenceContent(int idVal1In, int idVal2In) {
idVal1 = idVal1In; idVal2 = idVal2In;}
// Allow extrapolation beyond boundaries. This is optional.
virtual void setExtrapolate(bool) {}
// Read out parton density
double xf(int id, double x, double Q2);
// Read out valence and sea part of parton densities.
double xfVal(int id, double x, double Q2);
double xfSea(int id, double x, double Q2);
protected:
// Store relevant quantities.
int idBeam, idBeamAbs, idSav, idVal1, idVal2;
double xSav, Q2Sav;
double xu, xd, xs, xubar, xdbar, xsbar, xc, xb, xg, xlepton, xgamma,
xuVal, xuSea, xdVal, xdSea;
bool isSet, isInit;
// Resolve valence content for assumed meson. Possibly modified later.
void setValenceContent();
// Update parton densities.
virtual void xfUpdate(int id, double x, double Q2) = 0;
};
//==========================================================================
// Provide interface to the LHAPDF library of parton densities.
class LHAPDF : public PDF {
public:
// Constructor.
LHAPDF(int idBeamIn, string setName, int member, int nSetIn = 1,
Info* infoPtr = 0) : PDF(idBeamIn), nSet(nSetIn)
{init( setName, member, infoPtr);}
// Allow extrapolation beyond boundaries. This is optional.
void setExtrapolate(bool extrapol);
// Find out the nSet number corresponding to a name and member.
// Returns -1 if no such LHAPDF set has been initialized.
static int findNSet(string setName, int member);
// Return the lowest non-occupied nSet number.
static int freeNSet();
private:
// Initialization of PDF set.
void init(string setName, int member, Info* infoPtr);
// Update all PDF values.
void xfUpdate(int , double x, double Q2);
// Current set and pdf values.
int nSet;
double xfArray[13];
bool hasPhoton;
double xPhoton;
// Keep track of what sets have been initialized in LHAPDFInterface.
// The key is the nSet index, the value is a pair (name, member number).
static map< int, pair<string, int> > initializedSets;
};
//==========================================================================
// Gives the GRV 94L (leading order) parton distribution function set
// in parametrized form. Authors: M. Glueck, E. Reya and A. Vogt.
class GRV94L : public PDF {
public:
// Constructor.
GRV94L(int idBeamIn = 2212) : PDF(idBeamIn) {}
private:
// Update PDF values.
void xfUpdate(int , double x, double Q2);
// Auxiliary routines used during the updating.
double grvv (double x, double n, double ak, double bk, double a,
double b, double c, double d);
double grvw (double x, double s, double al, double be, double ak,
double bk, double a, double b, double c, double d, double e, double es);
double grvs (double x, double s, double sth, double al, double be,
double ak, double ag, double b, double d, double e, double es);
};
//==========================================================================
// Gives the CTEQ 5L (leading order) parton distribution function set
// in parametrized form. Parametrization by J. Pumplin. Authors: CTEQ.
class CTEQ5L : public PDF {
public:
// Constructor.
CTEQ5L(int idBeamIn = 2212) : PDF(idBeamIn) {}
private:
// Update PDF values.
void xfUpdate(int , double x, double Q2);
};
//==========================================================================
// The MSTWpdf class.
// MRST LO*(*) and MSTW 2008 PDF's, specifically the LO one.
// Original C++ version by Jeppe Andersen.
// Modified by Graeme Watt <watt(at)hep.ucl.ac.uk>.
// Sets available:
// iFit = 1 : MRST LO* (2007).
// iFit = 2 : MRST LO** (2008).
// iFit = 3 : MSTW 2008 LO, central member.
// iFit = 4 : MSTW 2008 NLO, central member. (Warning!)
class MSTWpdf : public PDF {
public:
// Constructor.
MSTWpdf(int idBeamIn = 2212, int iFitIn = 1, string xmlPath = "../xmldoc/",
Info* infoPtr = 0) : PDF(idBeamIn) {init( iFitIn, xmlPath, infoPtr);}
private:
// Constants: could only be changed in the code itself.
static const int np, nx, nq, nqc0, nqb0;
static const double xmin, xmax, qsqmin, qsqmax, xxInit[65], qqInit[49];
// Data read in from grid file or set at initialization.
int iFit, alphaSorder, alphaSnfmax;
double mCharm, mBottom, alphaSQ0, alphaSMZ, distance, tolerance,
xx[65], qq[49], c[13][64][48][5][5];
// Initialization of data array.
void init( int iFitIn, string xmlPath, Info* infoPtr);
// Update PDF values.
void xfUpdate(int , double x, double Q2);
// Evaluate PDF of one flavour species.
double parton(int flavour,double x,double q);
double parton_interpolate(int flavour,double xxx,double qqq);
double parton_extrapolate(int flavour,double xxx,double qqq);
// Auxiliary routines for evaluation.
int locate(double xx[],int n,double x);
double polderivative1(double x1, double x2, double x3, double y1,
double y2, double y3);
double polderivative2(double x1, double x2, double x3, double y1,
double y2, double y3);
double polderivative3(double x1, double x2, double x3, double y1,
double y2, double y3);
};
//==========================================================================
// The CTEQ6pdf class.
// Sets available:
// iFit = 1 : CTEQ6L
// iFit = 2 : CTEQ6L1
// iFit = 3 : CTEQ66.00 (NLO, central member)
// iFit = 4 : CT09MC1
// iFit = 5 : CT09MC2
// iFit = 6 : CT09MCS (not yet implemented)
class CTEQ6pdf : public PDF {
public:
// Constructor.
CTEQ6pdf(int idBeamIn = 2212, int iFitIn = 1, string xmlPath = "../xmldoc/",
Info* infoPtr = 0) : PDF(idBeamIn) {init( iFitIn, xmlPath, infoPtr);}
private:
// Constants: could only be changed in the code itself.
static const double EPSILON, XPOWER;
// Data read in from grid file or set at initialization.
int iFit, order, nQuark, nfMx, mxVal, nX, nT, nG,
iGridX, iGridQ, iGridLX, iGridLQ;
double lambda, mQ[7], qIni, qMax, tv[26], xMin, xv[202], upd[57773],
xvpow[202], xMinEps, xMaxEps, qMinEps, qMaxEps, fVec[5],
tConst[9], xConst[9], xLast, qLast;
// Initialization of data array.
void init( int iFitIn, string xmlPath, Info* infoPtr);
// Update PDF values.
void xfUpdate(int id, double x, double Q2);
// Evaluate PDF of one flavour species.
double parton6(int iParton, double x, double q);
// Interpolation in grid.
double polint4F(double xgrid[], double fgrid[], double xin);
};
//==========================================================================
// SA Unresolved proton: equivalent photon spectrum from
// V.M. Budnev, I.F. Ginzburg, G.V. Meledin and V.G. Serbo,
// Phys. Rept. 15 (1974/1975) 181.
class ProtonPoint : public PDF {
public:
// Constructor.
ProtonPoint(int idBeamIn = 2212, Info* infoPtrIn = 0) :
PDF(idBeamIn), m_infoPtr(infoPtrIn) {}
private:
// Stored value for PDF choice.
static const double ALPHAEM, Q2MAX, Q20, A, B, C;
// Update PDF values.
void xfUpdate(int , double x, double Q2);
// phi function from Q2 integration.
double phiFunc(double x, double Q);
// Info and errors
Info* m_infoPtr;
};
//==========================================================================
// Gives the GRV 1992 pi+ (leading order) parton distribution function set
// in parametrized form. Authors: Glueck, Reya and Vogt.
class GRVpiL : public PDF {
public:
// Constructor.
GRVpiL(int idBeamIn = 221) : PDF(idBeamIn) {}
private:
// Update PDF values.
void xfUpdate(int , double x, double Q2);
};
//==========================================================================
// Gives generic Q2-independent Pomeron PDF.
class PomFix : public PDF {
public:
// Constructor.
PomFix(int idBeamIn = 990, double PomGluonAIn = 0.,
double PomGluonBIn = 0., double PomQuarkAIn = 0.,
double PomQuarkBIn = 0., double PomQuarkFracIn = 0.,
double PomStrangeSuppIn = 0.) : PDF(idBeamIn),
PomGluonA(PomGluonAIn), PomGluonB(PomGluonBIn),
PomQuarkA(PomQuarkAIn), PomQuarkB(PomQuarkBIn),
PomQuarkFrac(PomQuarkFracIn), PomStrangeSupp(PomStrangeSuppIn)
{init();}
private:
// Stored value for PDF choice.
double PomGluonA, PomGluonB, PomQuarkA, PomQuarkB, PomQuarkFrac,
PomStrangeSupp, normGluon, normQuark;
// Initialization of some constants.
void init();
// Update PDF values.
void xfUpdate(int , double x, double);
};
//==========================================================================
// The H1 2006 Fit A and Fit B Pomeron parametrization.
// H1 Collaboration, A. Aktas et al., "Measurement and QCD Analysis of
// the Diffractive Deep-Inelastic Scattering Cross Section at HERA",
// DESY-06-049, Eur. Phys. J. C48 (2006) 715. e-Print: hep-ex/0606004.
class PomH1FitAB : public PDF {
public:
// Constructor.
PomH1FitAB(int idBeamIn = 990, int iFit = 1, double rescaleIn = 1.,
string xmlPath = "../xmldoc/", Info* infoPtr = 0) : PDF(idBeamIn)
{rescale = rescaleIn; init( iFit, xmlPath, infoPtr);}
private:
// Limits for grid in x, in Q2, and data in (x, Q2).
int nx, nQ2;
double rescale, xlow, xupp, dx, Q2low, Q2upp, dQ2;
double gluonGrid[100][30];
double quarkGrid[100][30];
// Initialization of data array.
void init( int iFit, string xmlPath, Info* infoPtr);
// Update PDF values.
void xfUpdate(int , double x, double );
};
//==========================================================================
// The H1 2007 Jets Pomeron parametrization..
// H1 Collaboration, A. Aktas et al., "Dijet Cross Sections and Parton
// Densities in Diffractive DIS at HERA", DESY-07-115, Aug 2007. 33pp.
// Published in JHEP 0710:042,2007. e-Print: arXiv:0708.3217 [hep-ex]
class PomH1Jets : public PDF {
public:
// Constructor.
PomH1Jets(int idBeamIn = 990, double rescaleIn = 1.,
string xmlPath = "../xmldoc/", Info* infoPtr = 0) : PDF(idBeamIn)
{rescale = rescaleIn; init( xmlPath, infoPtr);}
private:
// Arrays for grid in x, in Q2, and data in (x, Q2).
double rescale;
double xGrid[100];
double Q2Grid[88];
double gluonGrid[100][88];
double singletGrid[100][88];
double charmGrid[100][88];
// Initialization of data array.
void init( string xmlPath, Info* infoPtr);
// Update PDF values.
void xfUpdate(int id, double x, double );
};
//==========================================================================
// Gives electron (or muon, or tau) parton distribution.
class Lepton : public PDF {
public:
// Constructor.
Lepton(int idBeamIn = 11) : PDF(idBeamIn) {}
private:
// Constants: could only be changed in the code itself.
static const double ALPHAEM, ME, MMU, MTAU;
// Update PDF values.
void xfUpdate(int id, double x, double Q2);
// The squared lepton mass, set at initialization.
double m2Lep;
};
//==========================================================================
// Gives electron (or other lepton) parton distribution when unresolved.
class LeptonPoint : public PDF {
public:
// Constructor.
LeptonPoint(int idBeamIn = 11) : PDF(idBeamIn) {}
private:
// Update PDF values in trivial way.
void xfUpdate(int , double , double ) {xlepton = 1; xgamma = 0.;}
};
//==========================================================================
// Gives neutrino parton distribution when unresolved (only choice for now).
// Note factor of 2 since only lefthanded implies no spin averaging.
class NeutrinoPoint : public PDF {
public:
// Constructor.
NeutrinoPoint(int idBeamIn = 12) : PDF(idBeamIn) {}
private:
// Update PDF values, with spin factor of 2.
void xfUpdate(int , double , double ) {xlepton = 2; xgamma = 0.;}
};
//==========================================================================
// The NNPDF class.
// Sets available:
// Leading order QCD+QED Proton PDF sets
// iFit = 1 : NNPDF2.3 QCD+QED LO, alphas(MZ) = 0.130
// iFit = 2 : NNPDF2.3 QCD+QED LO, alphas(MZ) = 0.119
// (Next-to-)Next-to-Leading order QCD+QED Proton PDF sets
// iFit = 3 : NNPDF2.3 QCD+QED NLO, alphas(MZ) = 0.119
// iFit = 4 : NNPDF2.3 QCD+QED NNLO, alphas(MZ) = 0.119
// Code provided by Juan Rojo and Stefano Carrazza.
class NNPDF : public PDF {
public:
// Constructor.
NNPDF(int idBeamIn = 2212, int iFitIn = 1, string xmlPath = "../xmldoc/",
Info* infoPtr = 0) : PDF(idBeamIn), fPDFGrid(NULL), fXGrid(NULL),
fLogXGrid(NULL), fQ2Grid(NULL), fLogQ2Grid(NULL), fRes(NULL) {
init( iFitIn, xmlPath, infoPtr); };
// Destructor.
~NNPDF() {
if (fPDFGrid) {
for (int i = 0; i < fNFL; i++) {
for (int j = 0; j < fNX; j++)
if (fPDFGrid[i][j]) delete[] fPDFGrid[i][j];
if (fPDFGrid[i]) delete[] fPDFGrid[i];
}
delete[] fPDFGrid;
}
if (fXGrid) delete[] fXGrid;
if (fLogXGrid) delete[] fLogXGrid;
if (fQ2Grid) delete[] fQ2Grid;
if (fLogQ2Grid) delete[] fLogQ2Grid;
if (fRes) delete[] fRes;
};
private:
// Constants: could only be changed in the code itself.
static const double fXMINGRID;
// Number of flavors (including photon) and interpolation parameters.
static const int fNFL = 14;
static const int fM = 4;
static const int fN = 2;
// Variables to be set during code initialization.
int iFit, fNX, fNQ2;
double ***fPDFGrid;
double *fXGrid;
double *fLogXGrid;
double *fQ2Grid;
double *fLogQ2Grid;
double *fRes;
// Initialization of data array.
void init( int iFitIn, string xmlPath, Info* infoPtr);
// Update PDF values.
void xfUpdate(int id, double x, double Q2);
// Interpolation in the grid for a given PDF flavour.
void xfxevolve(double x, double Q2);
// 1D and 2D polynomial interpolation.
void polint(double xa[], double ya[], int n, double x,
double& y, double& dy);
void polin2(double x1a[], double x2a[], double ya[][fN],
double x1, double x2, double& y, double& dy);
};
//==========================================================================
} // end namespace Pythia8
#endif // Pythia8_PartonDistributions_H
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