deps/mstwpdf/mstwpdf.h

0001 /////////////////////////////////////////////////////////////////////
0002 // Class header file for MSTW PDFs.
0003 // Original C++ version by Jeppe Andersen.
0004 // Modified by Graeme Watt <Graeme.Watt(at)cern.ch>.
0005 // Updated 25/06/2010: Enlarge allowed range for m_c and m_b.
0006 //
0007 // Usage:
0008 // Initialising an instance of the class:
0009 //   c_mstwpdf pdf("filename.dat")
0010 // with "filename.dat" being the data file to interpolate.
0011 //
0012 // A call to the method
0013 //   c_mstwpdf::update(x,q)
0014 // updates the parton content to the values at (x,q^2).
0015 // The parton contents can then be accessed in
0016 //   c_mstwpdf::cont.upv etc.
0017 // This method is faster if all the flavours need to be evaluated.
0018 //
0019 // A call to the method
0020 //   c_mstwpdf::parton(f,x,q)
0021 // will return the value of the PDF with flavour 'f' at (x,q^2).
0022 // Now use PDG notation for parton flavour (apart from gluon=0, not 21):
0023 //  f =   -6,  -5,  -4,  -3,  -2,  -1,0,1,2,3,4,5,6
0024 //    = tbar,bbar,cbar,sbar,ubar,dbar,g,d,u,s,c,b,t.
0025 // Can also get valence quarks directly:
0026 //  f =  7, 8, 9,10,11,12
0027 //    = dv,uv,sv,cv,bv,tv.
0028 // Photon: f = 13.
0029 // This method is faster if only one flavour needs to be evaluated.
0030 /////////////////////////////////////////////////////////////////////
0031
0032 #include <istream>
0033
0034 #ifndef _MSTWPDF_H_INCLUDED_
0035 #define _MSTWPDF_H_INCLUDED_
0036
0037 namespace mstw {
0038
0039 class c_mstwpdf {
0040  private:
0041   const static int np=12;   // number of parton flavours
0042   const static int nx=64;   // number of x grid points
0043   const static int nq=48;   // number of q^2 grid points
0044   int nqc0; // number of q^2 bins below charm threshold
0045   int nqb0; // number of q^2 bins below bottom threshold
0046   static double xx[nx+1];   // grid points in x
0047   static double qq[nq+1];   // grid points in q^2
0048   double c[np+1][nx][nq][5][5]; // coefficients used for interpolation
0049   double parton_interpolate(int flavour,double xxx,double qqq) const;
0050   double parton_extrapolate(int flavour,double xxx,double qqq) const;
0051   bool extrapolate;
0052   bool fatal;
0053   void init(std::istream& data_file,bool extrapolate,bool fatal,char const* filename);
0054  public:
0055   struct s_partoncontent {
0056     double upv,dnv,usea,dsea,str,sbar,chm,cbar,bot,bbar,glu,phot;
0057   } cont;
0058   double xmin,xmax,qsqmin,qsqmax;
0059   double mCharm,mBottom,alphaSQ0,alphaSMZ;
0060   double distance,tolerance;
0061   int alphaSorder,alphaSnfmax;
0062   void update(double x,double q); // update cont
0063   double parton(int flavour,double x,double q) const;
0064   // The constructor (initialises the functions):
0065   c_mstwpdf(char const* filename,bool extrapolate=false,bool fatal=true);
0066   c_mstwpdf(std::istream& data_file, bool extrapolate=false, bool fatal=true);
0067 };
0068
0069 }
0070
0071 #endif