5 * Revision 1.1.1.5 2000/04/19 13:27:52 mclareni
8 * Revision 1.1.1.1 1996/04/12 15:29:08 plothow
12 #include "pdf/pilot.h"
13 FUNCTION Ctq1pf (ISET, IPARTON, X, Q, IRT)
15 C CTEQ distribution function in a parametrized form.
17 C (No data tables are needed.)
19 C The returned function value is the PROBABILITY density for a given FLAVOR.
21 C !! A companion function (next module), which this one depends on,
22 C !! ctq1pd (Iset, Iparton, X, Q, Irt)
23 C !! gives the VALENCE and SEA MOMENTUM FRACTION distributions.
25 C \\ A parallel (independent) program Ctq1Ps (not included in this file)
26 C || in Subroutine form is also available.
27 C || It returns ALL the parton flavors at once in an array form.
28 C // See details in that separate file if you are interested.
30 C Ref.: "CTEQ Parton Distributions and Flavor Dependence of the Sea Quarks"
31 C by: J. Botts, J.G. Morfin, J.F. Owens, J. Qiu, W.K. Tung & H. Weerts
32 C MSUHEP-92-27, Fermilab-Pub-92/371, FSU-HEP-92-1225, ISU-NP-92-17
34 C Since this is an initial distribution, and there may be updates, it is
35 C useful for the authors to maintain a record of the distribution list.
36 C Please do not freely distribute this program package; instead, refer any
37 C interested colleague to direct their request for a copy to:
38 C Botts@msupa.pa.msu.edu or Botts@msupa (bitnet) or MSUHEP::Botts
40 C If you have any questions concerning these distributions, direct inquires
41 C to Jim Botts or Wu-Ki Tung (username Tung at same E-mail nodes as above).
45 CRevision 1.1.1.5 2000/04/19 13:27:52 mclareni
48 CRevision 1.1.1.1 1996/04/12 15:29:08 plothow
51 C Revision 1.2 93/02/26 10:42:43 wkt
52 C Version with heavy quark threshold factor and faster algorithm.
54 C Revision 1.1 93/02/14 17:30:21 botts
55 C The new Faster version.
56 C Revision 1.0 93/02/08 18:35:25 wkt
59 C This function returns the CTEQ parton distributions f^Iset_Iprtn/proton
60 C where Iset (= 1, 2, ..., 5) is the set label;
62 C Name convention for CTEQ distributions: CTEQnSx where
63 C n : version number (currently n = 1)
64 C S : factorization scheme label: = [M D L] for [MS-bar DIS LO]
66 C x : special characteristics, if any
67 C (e.g. S for singular gluon, L for "LEP lambda value")
69 C Iprtn is the parton label (6, 5, 4, 3, 2, 1, 0, -1, ......, -6)
70 C for (t, b, c, s, d, u, g, u_bar, ..., t_bar)
72 C X, Q are the usual x, Q; Irt is a return error code (not implemented yet).
74 C --> Iset = 1, 2, 3, 4, 5 correspond to the following CTEQ global fits:
75 C cteq1M, cteq1MS, cteq1ML, cteq1D, cteq1L respectively.
77 C --> QCD parameters for parton distribution set Iset can be obtained inside
78 C the user's program by:
80 C > (Iset, Iord, Ischeme, MxFlv,
81 C > Alam4, Alam5, Alam6, Amas4, Amas5, Amas6,
82 C > Xmin, Qini, Qmax, ExpNor)
83 C where all but the first argument are output parameters.
84 C They should be self-explanary -- see details in next module.
86 C The range of (x, Q) used in this round of global analysis is, approxi-
87 C mately, 0.01 < x < 0.75 ; and 4 GeV^2 < Q^2 < 400 GeV^2.
89 C The range of (x, Q) used in the reparametrization of the QCD evolved
90 C parton distributions is 10E-5 < x < 1 ; 2 GeV < Q < 1 TeV. The
91 C functional form of this parametrization is:
93 C A0 * x^A1 * (1-x)^A2 * (1 + A3 * x^A4) * [log(1+1/x)]^A5
95 C with the A'coefficients being smooth functions of Q. For heavy quarks,
96 C an additional threshold factor is applied which simulate the Q-dependence
97 C of the QCD evolution in that region.
99 C Since this function is positive definite and smooth, it provides sensible
100 C extrapolations of the parton distributions if they are called beyond
101 C the original range in an application. There is no artificial boundaries
104 C IMPLICIT DOUBLE PRECISION (A-H, O-Z)
113 ELSEIF (IFL .LE. 2) THEN
114 VL = Ctq1Pd (ISET, IFL, X, Q, IRT)
119 SEA = Ctq1Pd (ISET, -JFL, X, Q, IRT)
120 C Full (probability) Distribution
121 Ctq1pf = (VL + SEA) / X
124 C *************************