PDF/spdf/whit4g.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.2  1996/10/30 08:32:03  cernlib
   6 * Version 7.04
   7 *
   8 * Revision 1.1.1.1  1996/04/12 15:30:16  plothow
   9 * Version 7.01
  10 *
  11 *
  12 #include "pdf/pilot.h"
  13 c
  14 ccccccccccccccccccccccccccccccccccccccccccccccccccccccc
  15       DOUBLE PRECISION function WHIT4G(x,Q2)
  16 c               input: x,Q2
  17 c               output: clg
  18 c                        (gluon dist.)
  19 ccccccccccccccccccccccccccccccccccccccccccccccccccccccc
  20       implicit none
  21 c arg
  22       DOUBLE PRECISION Q2,x
  23 c const
  24       DOUBLE PRECISION q42it,q52it,lam42,lam52
  25       DOUBLE PRECISION alinv
  26 c local
  27       DOUBLE PRECISION A0g,B0g,C0g,A1g,AA1g,B1g,C1g
  28       DOUBLE PRECISION s,s2,s3,s4,prsccf
  29       DOUBLE PRECISION x1
  30 c parameters
  31       parameter(lam42=0.16d0, lam52=0.091411319d0)
  32       parameter(Q42IT=4.0d0, Q52IT=100.0d0)
  33       parameter(alinv=137.036d0)
  34       common /scale/ s,s2,s3,s4,prsccf
  35 c
  36 c begin
  37       x1=1.0d0-x
  38 c
  39       if(Q2.lt.100.0d0) then
  40 c  under 100 GeV^2
  41 c
  42 cccccc   WHIT4 gluon (U100)
  43 c
  44       A0g = 4.000000d+00+s*(-9.400000d+00)+s2*( 1.555000d+01)
  45      $          +s3*(-1.450000d+01)+s4*( 5.470000d+00)
  46       B0g =              s*(-1.142000d+00)+s2*( 1.034000d+00)
  47      $          +s3*(-4.410000d-01)
  48       C0g = 3.000000d+00+s*( 8.720000d-01)+s2*( 1.006000d+00)
  49      $          +s3*( 3.560000d-01)
  50       A1g =              s*( 6.020000d-01)+s2*( 5.090000d-01)
  51      $          +s3*(-2.054000d+00)+s4*( 1.392000d+00)
  52       AA1g=              s*(-9.220000d-02)+s2*(-1.899000d+00)
  53      $          +s3*( 4.180000d+00)+s4*(-2.494000d+00)
  54       B1g =-2.895000d-01+s*( 3.760000d-01)+s2*(-1.719000d+00)
  55      $          +s3*( 1.116000d+00)
  56       C1g = 1.439000d+00+s*(-5.570000d-01)+s2*( 3.660000d-01)
  57      $          +s3*( 7.330000d-01)+s4*(-7.620000d-01)
  58       else
  59 c over 100 GeV^2
  60 c
  61 cccccc   WHIT4 gluon (O100)
  62 c
  63       A0g = 1.384000d+00+s*(-2.455000d+00)+s2*( 8.940000d+00)
  64      $          +s3*(-2.906000d+01)+s4*( 3.710000d+01)
  65       B0g =-4.420000d-01+s*(-7.190000d-01)+s2*( 2.961000d+00)
  66      $          +s3*(-1.209000d+01)+s4*( 1.916000d+01)
  67       C0g = 4.210000d+00+s*( 2.524000d+00)+s2*( 1.003000d+01)
  68      $          +s3*(-1.827000d+01)+s4*( 2.162000d+00)
  69       A1g = 2.992000d-01+s*( 1.179000d+00)+s2*(-1.915000d+00)
  70      $          +s3*( 7.260000d+00)+s4*(-1.839000d+01)
  71       AA1g=-1.600000d-01+s*(-1.114000d+00)+s2*( 2.939000d+00)
  72      $          +s3*(-6.660000d+00)+s4*( 1.923000d+01)
  73       B1g =-4.830000d-01+s*( 7.550000d-01)+s2*(-3.800000d+00)
  74      $          +s3*( 1.075000d+01)+s4*(-1.993000d+01)
  75       C1g = 1.297000d+00+s*(-1.669000d-01)+s2*( 1.906000d+00)
  76      $          +s3*(-2.057000d+00)
  77       endif
  78 c
  79          WHIT4G = prsccf/alinv/x*
  80      $            ( A0g * x**B0g * x1**C0g
  81      $             +(A1g+AA1g*x) * x**B1g * x1**C1g )
  82 c
  83       return
  84       end