dd/daf/ctq5pdf_8F_source.html

C============================================================================

C                CTEQ Parton Distribution Functions: Version 5.0

C                             Nov. 1, 1999

C

C   Ref: "GLOBAL QCD ANALYSIS OF PARTON STRUCTURE OF THE NUCLEON:

C         CTEQ5 PPARTON DISTRIBUTIONS"

C

C  hep-ph/9903282; to be published in Eur. Phys. J. C 1999.

C

C  These PDF's use quadratic interpolation of attached tables. A parametrized

C  version of the same PDF's without external tables is under construction.

C  They will become available later.

C

C   This package contains 7 sets of CTEQ5 PDF's; plus two updated ones.

C   The undated CTEQ5M1 and CTEQHQ1 use an improved evolution code.

C   Both the original and the updated ones fit current data with comparable

C   accuracy.  The CTEQHQ1 set also involve a different choice of scale,

C   hence differs from CTEQHQ slightly more.  It is preferred over CTEQ5HQ.


C   Details are:

C ---------------------------------------------------------------------------

C  Iset   PDF        Description       Alpha_s(Mz)  Lam4  Lam5   Table_File

C ---------------------------------------------------------------------------

C x 1    CTEQ5M   Standard MSbar scheme   0.118     326   226    cteq5m.tbl

C   2    CTEQ5D   Standard DIS scheme     0.118     326   226    cteq5d.tbl

C x 3    CTEQ5L   Leading Order           0.127     192   146    cteq5l.tbl

C   4    CTEQ5HJ  Large-x gluon enhanced  0.118     326   226    cteq5hj.tbl

C   5    CTEQ5HQ  Heavy Quark             0.118     326   226    cteq5hq.tbl

C   6    CTEQ5F3  Nf=3 FixedFlavorNumber  0.106     (Lam3=395)   cteq5f3.tbl

C   7    CTEQ5F4  Nf=4 FixedFlavorNumber  0.112     309   XXX    cteq5f4.tbl

C         --------------------------------------------------------

C x 8    CTEQ5M1  Improved CTEQ5M         0.118     326   226    cteq5m1.tbl

C   9    CTEQ5HQ1 Improved CTEQ5HQ        0.118     326   226    ctq5hq1.tbl

C ---------------------------------------------------------------------------

C

C  The available applied range is 10^-5 << x << 1 and 1.0 << Q << 10,000 (GeV).

C   Lam5 (Lam4, Lam3) represents Lambda value (in MeV) for 5 (4,3) flavors.

C   The matching alpha_s between 4 and 5 flavors takes place at Q=4.5 GeV,

C   which is defined as the bottom quark mass, whenever it can be applied.

C

C   The Table_Files are assumed to be in the working directory.

C

C   Before using the PDF, it is necessary to do the initialization by

C       Call SetCtq5(Iset)

C   where Iset is the desired PDF specified in the above table.

C

C   The function Ctq5Pdf (Iparton, X, Q)

C   returns the parton distribution inside the proton for parton [Iparton]

C   at [X] Bjorken_X and scale [Q] (GeV) in PDF set [Iset].

C   Iparton  is the parton label (5, 4, 3, 2, 1, 0, -1, ......, -5)

C                            for (b, c, s, d, u, g, u_bar, ..., b_bar),

C      whereas CTEQ5F3 has, by definition, only 3 flavors and gluon;

C              CTEQ5F4 has only 4 flavors and gluon.

C

C   For detailed information on the parameters used, e.q. quark masses,

C   QCD Lambda, ... etc.,  see info lines at the beginning of the

C   Table_Files.

C

C   These programs, as provided, are in double precision.  By removing the

C   "Implicit Double Precision" lines, they can also be run in single

C   precision.

C

C   If you have detailed questions concerning these CTEQ5 distributions,

C   or if you find problems/bugs using this package, direct inquires to

C   Hung-Liang Lai(lai@phys.nthu.edu.tw) or Wu-Ki Tung(Tung@pa.msu.edu).

C

C===========================================================================


      Function ctq5pdf (Iparton, X, Q)

      Implicit Double Precision (a-h,o-z)

      Logical warn

      Common

     > / ctqpar2 / nx, nt, nfmx

     > / qcdtable /  alambda, nfl, iorder


      Data warn /.true./

      save warn


      If (x .lt. 0d0 .or. x .gt. 1d0) Then

  print *, 'X out of range in Ctq5Pdf: ', x

  stop

      Endif

      If (q .lt. alambda) Then

        print *, 'Q out of range in Ctq5Pdf: ', q

        stop

      Endif

      If ((iparton .lt. -nfmx .or. iparton .gt. nfmx)) Then

        If (warn) Then

C        put a warning for calling extra flavor.

       warn = .false.

       print *, 'Warning: Iparton out of range in Ctq5Pdf: '

     >              , iparton

         Endif

         ctq5pdf = 0d0

         Return

      Endif


      ctq5pdf = partonx5(iparton, x, q)

      if(ctq5pdf.lt.0.d0)  ctq5pdf = 0.d0


      Return

C                             ********************

      End