]>
Commit | Line | Data |
---|---|---|
21886bb6 | 1 | #include "pdf/pilot.h" |
2 | C CTEQ5M1 and CTEQ5L Parton Distribution Functions in Parametrized Form | |
3 | C | |
4 | C September 15, 1999 | |
5 | C | |
6 | C Ref: "GLOBAL QCD ANALYSIS OF PARTON STRUCTURE OF THE NUCLEON: | |
7 | C CTEQ5 PPARTON DISTRIBUTIONS" | |
8 | C hep-ph/9903282 | |
9 | C | |
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 | |
13 | C all applications. | |
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. | |
16 | C | |
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. | |
19 | C | |
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. | |
23 | C | |
24 | C These parametrizations were obtained by Jon Pumplin. | |
25 | C | |
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. | |
34 | C | |
35 | C The two Iset value are adopted to agree with the standard table versions. | |
36 | C | |
37 | C The following user-callable routines are provided: | |
38 | C | |
39 | C FUNCTION Ctq5Pd (Iset, Iprtn, X, Q, Irt) | |
40 | C returns the PROBABILITY density for a GIVEN flavor; | |
41 | C | |
42 | C FUNCTION Ctq5df (Iset, Iprtn, X, Q, Irt) | |
43 | C returns the MOMENTUM density of a GIVEN valence or sea distribution. | |
44 | C | |
45 | C SUBROUTINE Ctq5Pds(Iset, Pdf, X, Q, Irt) | |
46 | C returns an array of MOMENTUM densities for ALL flavors; | |
47 | C | |
48 | C The arguments of these routines are as follows: | |
49 | C | |
50 | C Iset is the set number: 1 for CTEQ5M1 or 3 for CTEQ5L | |
51 | C | |
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. | |
56 | C | |
57 | C X, Q are the usual x, Q; | |
58 | C | |
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. | |
61 | C | |
62 | C Range of validity: | |
63 | C | |
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. | |
68 | C | |
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. | |
73 | C | |
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. | |
77 | C | |
78 | C ************************************************************************** | |
79 | 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" | |
87 | integer ifl | |
88 | ||
89 | ii = ifl | |
90 | if(ii .gt. 2) then | |
91 | ii = -ii | |
92 | endif | |
93 | ||
94 | if(ii .eq. -1) then | |
95 | sum = faux5MI(-1,x,q) | |
96 | ratio = faux5MI(-2,x,q) | |
97 | ctq5MI = sum/(1.d0 + ratio) | |
98 | ||
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) | |
103 | ||
104 | elseif(ii .ge. -5) then | |
105 | ctq5MI = faux5MI(ii,x,q) | |
106 | ||
107 | else | |
108 | ctq5MI = 0.d0 | |
109 | ||
110 | endif | |
111 | ||
112 | return | |
113 | end |