2 C CTEQ5M1 and CTEQ5L Parton Distribution Functions in Parametrized Form
6 C Ref: "GLOBAL QCD ANALYSIS OF PARTON STRUCTURE OF THE NUCLEON:
7 C CTEQ5 PPARTON DISTRIBUTIONS"
10 C The CTEQ5M1 set given here is an updated version of the original CTEQ5M
11 C set posted, in the table version, on the Web page of CTEQ.
12 C The differences between CTEQ5M and CTEQ5M1 are insignificant for almost
14 C The improvement is in the QCD evolution which is now more accurate, and
15 C which agrees completely with the benchmark work of the HERA 96/97 Workshop.
17 C The differences between the parametrized and the corresponding table ver-
18 C sions (on which it is based) are of similar order as between the two version.
20 C!! Because accurate parametrizations over a wide range of (x,Q) is hard to
21 C obtain, only the most widely used sets CTEQ5M and CTEQ5L are available
22 C in parametrized form for now.
24 C These parametrizations were obtained by Jon Pumplin.
26 C ******************************
27 C Iset PDF Description Alpha_s(Mz) Lam4 Lam5
28 C ---------------------------------------------------------------------------
29 C 1 CTEQ5M1 Standard NLO MSbar scheme 0.118 326 226
30 C 3 CTEQ5L Leading Order 0.127 192 146
31 C ---------------------------------------------------------------------------
32 C Note the Qcd-lambda values given for CTEQ5L is for the leading order
33 C form of Alpha_s!! Alpha_s(Mz) gives the absolute calibration.
35 C The two Iset value are adopted to agree with the standard table versions.
37 C The following user-callable routines are provided:
39 C FUNCTION Ctq5Pd (Iset, Iprtn, X, Q, Irt)
40 C returns the PROBABILITY density for a GIVEN flavor;
42 C FUNCTION Ctq5df (Iset, Iprtn, X, Q, Irt)
43 C returns the MOMENTUM density of a GIVEN valence or sea distribution.
45 C SUBROUTINE Ctq5Pds(Iset, Pdf, X, Q, Irt)
46 C returns an array of MOMENTUM densities for ALL flavors;
48 C The arguments of these routines are as follows:
50 C Iset is the set number: 1 for CTEQ5M1 or 3 for CTEQ5L
52 C Iprtn is the parton label (6, 5, 4, 3, 2, 1, 0, -1, ......, -6)
53 C for (t, b, c, s, d, u, g, u_bar, ..., t_bar)
54 C *** WARNING: We use the parton label 2 as D-quark and 1 as U-quark,
55 C which might be different from your labels.
57 C X, Q are the usual x, Q;
59 C Irt is an error code: 0 if there was no error; 1 or more if (x,q) was
60 C outside the range of validity of the parametrization.
64 C The range of (x, Q) covered by this parametrization of the QCD evolved
65 C parton distributions is 1E-6 < x < 1 ; 1.1 GeV < Q < 10 TeV. Of course,
66 C the PDF's are constrained by data only in a subset of that region; and
67 C the assumed DGLAP evolution is unlikely to be valid for all of it either.
69 C The range of (x, Q) used in the CTEQ5 round of global analysis is
70 C approximately 0.01 < x < 0.75 ; and 4 GeV^2 < Q^2 < 400 GeV^2 for
71 C fixed target experiments; 0.0001 < x < 0.3 from HERA data; and
72 C Q^2 up to 40,000 GeV^2 from Tevatron inclusive Jet data.
74 C DOUBLE PRECISION is used throughout in these routines, but conversion to
75 C SINGLE PRECISION is possible
76 C by removing the Implicit Double Precision statements.
78 C **************************************************************************
80 C ********************************************************
81 c --------------------------------------------------------------------------
82 double precision function ctq5MI(ifl,x,q)
83 c Parametrization of cteq5MI parton distribution functions (J. Pumplin 9/99).
84 c ifl: 1=u,2=d,3=s,4=c,5=b;0=gluon;-1=ubar,-2=dbar,-3=sbar,-4=cbar,-5=bbar.
85 c --------------------------------------------------------------------------
86 #include "pdf/impdp.inc"
96 ratio = faux5MI(-2,x,q)
97 ctq5MI = sum/(1.d0 + ratio)
99 elseif(ii .eq. -2) then
100 sum = faux5MI(-1,x,q)
101 ratio = faux5MI(-2,x,q)
102 ctq5MI = sum*ratio/(1.d0 + ratio)
104 elseif(ii .ge. -5) then
105 ctq5MI = faux5MI(ii,x,q)