5 * Revision 1.1.1.2 1996/10/30 08:32:04 cernlib
8 * Revision 1.1.1.1 1996/04/12 15:30:16 plothow
12 #include "pdf/pilot.h"
14 cccccccccccccccccccccccccccccc
16 subroutine WHIT4Q(x,r,cv,cs)
17 ccc INPUTS : x,r=mc^2/Q^2
18 ccc OUTPUTS: cv,cs (valence- and sea- charm quark dist)
19 ccc cv <-- cv / ( alpha / 2PI)
20 ccc cs <-- cs / ( alpha_s/2PI)
25 DOUBLE PRECISION cv,cs
27 DOUBLE PRECISION ec,mc
28 parameter(ec=2.0d0/3.0d0,mc=1.5d0)
29 c N=15 Gauss int. weights and points
32 DOUBLE PRECISION XG(GN), XW(GN)
33 DATA (XG(i),i=1,GN)/6.003741d-03,
34 $ 3.136330d-02, 7.589671d-02, 1.377911d-01, 2.145139d-01,
35 $ 3.029243d-01, 3.994030d-01, 5.000000d-01, 6.005970d-01,
36 $ 6.970757d-01, 7.854861d-01, 8.622089d-01, 9.241033d-01,
37 $ 9.686367d-01, 9.939963d-01/
38 DATA (XW(i),i=1,GN)/1.537662d-02,
39 $ 3.518302d-02, 5.357961d-02, 6.978534d-02, 8.313460d-02,
40 $ 9.308050d-02, 9.921574d-02, 1.012891d-01, 9.921574d-02,
41 $ 9.308050d-02, 8.313460d-02, 6.978534d-02, 5.357961d-02,
42 $ 3.518302d-02, 1.537662d-02/
44 DOUBLE PRECISION sum, y,z,beta,w,WHIT4G,L
46 DOUBLE PRECISION x1,rx,z1,rz
53 beta=dsqrt(1.0d0-rx/x1)
54 w=x*( beta*(-1.0d0+8.0d0*x*x1-rx*x1)
55 $ +(x**2+x1**2+rx*(1.0d0-3.0d0*x)-0.5d0*rx**2)
56 $ * log( (1.0d0+beta)/(1.0d0-beta) ))
57 cv = 3.0d0*ec**2 * w / x
62 y= x+rx + (x1-rx)*XG(i)**L
66 beta=dsqrt(1.0d0-rz/z1)
67 w=z*( beta*(-1.0d0+8.0d0*z*z1-rz*z1)
68 $ +(z**2+z1**2+rz*(1.0d0-3.0d0*z)-0.5d0*rz**2)
69 $ * log( (1.0d0+beta)/(1.0d0-beta) ))
71 sum= sum + w * WHIT4G(y,mc**2/r)* L*XG(i)**(L-1.0d0)*XW(i)
75 cs = 0.5d0/x * (x1-rx) * sum