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fe4da5cc | 1 | * |
2 | * $Id$ | |
3 | * | |
4 | * $Log$ | |
5 | * Revision 1.1.1.4 1997/07/13 13:22:35 cernlib | |
6 | * Import version 7.09 | |
7 | * | |
8 | * Revision 1.1.1.1 1996/04/12 15:29:08 plothow | |
9 | * Version 7.01 | |
10 | * | |
11 | * | |
12 | #include "pdf/pilot.h" | |
13 | FUNCTION Ctq1pf (ISET, IPARTON, X, Q, IRT) | |
14 | ||
15 | C CTEQ distribution function in a parametrized form. | |
16 | ||
17 | C (No data tables are needed.) | |
18 | ||
19 | C The returned function value is the PROBABILITY density for a given FLAVOR. | |
20 | ||
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. | |
24 | ||
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. | |
29 | ||
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 | |
33 | ||
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 | |
39 | ||
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). | |
42 | ||
43 | C$Header$ | |
44 | C$Log$ | |
45 | CRevision 1.1.1.4 1997/07/13 13:22:35 cernlib | |
46 | CImport version 7.09 | |
47 | C | |
48 | CRevision 1.1.1.1 1996/04/12 15:29:08 plothow | |
49 | CVersion 7.01 | |
50 | C | |
51 | C Revision 1.2 93/02/26 10:42:43 wkt | |
52 | C Version with heavy quark threshold factor and faster algorithm. | |
53 | C | |
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 | |
57 | C Initial revision | |
58 | ||
59 | C This function returns the CTEQ parton distributions f^Iset_Iprtn/proton | |
60 | C where Iset (= 1, 2, ..., 5) is the set label; | |
61 | ||
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] | |
65 | C resp. | |
66 | C x : special characteristics, if any | |
67 | C (e.g. S for singular gluon, L for "LEP lambda value") | |
68 | ||
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) | |
71 | ||
72 | C X, Q are the usual x, Q; Irt is a return error code (not implemented yet). | |
73 | ||
74 | C --> Iset = 1, 2, 3, 4, 5 correspond to the following CTEQ global fits: | |
75 | C cteq1M, cteq1MS, cteq1ML, cteq1D, cteq1L respectively. | |
76 | ||
77 | C --> QCD parameters for parton distribution set Iset can be obtained inside | |
78 | C the user's program by: | |
79 | C Dum = PrCtq1 | |
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. | |
85 | ||
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. | |
88 | ||
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: | |
92 | ||
93 | C A0 * x^A1 * (1-x)^A2 * (1 + A3 * x^A4) * [log(1+1/x)]^A5 | |
94 | ||
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. | |
98 | ||
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 | |
102 | C or sharp cutoff's. | |
103 | ||
104 | C IMPLICIT DOUBLE PRECISION (A-H, O-Z) | |
105 | C+SEQ, IMPDP. | |
106 | REAL Ctq1Pd,X,Q | |
107 | ||
108 | IFL = IPARTON | |
109 | JFL = ABS(IFL) | |
110 | C Valence | |
111 | IF (IFL .LE. 0) THEN | |
112 | VL = 0. | |
113 | ELSEIF (IFL .LE. 2) THEN | |
114 | VL = Ctq1Pd (ISET, IFL, X, Q, IRT) | |
115 | ELSE | |
116 | VL = 0. | |
117 | ENDIF | |
118 | C Sea | |
119 | SEA = Ctq1Pd (ISET, -JFL, X, Q, IRT) | |
120 | C Full (probability) Distribution | |
121 | Ctq1pf = (VL + SEA) / X | |
122 | ||
123 | RETURN | |
124 | C ************************* | |
125 | END |