GEANT321/gphys/gphsig.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:21:30  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 *CMZ :  3.21/02 29/03/94  15.41.22  by  S.Giani
  11 *-- Author :
  12       FUNCTION GPHSIG(Z,E)
  13 C.
  14 C.    ******************************************************************
  15 C.    *                                                                *
  16 C.    *       Function to compute the photoeffect total cross-section  *
  17 C.    *       as a function of Z and E                                 *
  18 C.    *           (E in GeV,  GPHSIG in barn)                          *
  19 C.    *                                                                *
  20 C.    *    ==>Called by : GPHOTI                                       *
  21 C.    *       Author : L.Urban   *********                             *
  22 C.    *                                                                *
  23 C.    ******************************************************************
  24 C.
  25 #include "geant321/gconsp.inc"
  26       DIMENSION EK(4),EL1(4),EL2(4),C(19)
  27       DATA EK / 0.66644E-8 , 0.22077E-9 ,-0.32552E-11, 0.18199E-13/
  28       DATA EL1/-0.29179E-9 , 0.87983E-10,-0.12589E-11, 0.69602E-14/
  29       DATA EL2/-0.68606E-9 , 0.10078E-9 ,-0.14496E-11, 0.78809E-14/
  30       DATA C  /-0.88893E-6 , 0.24394E-8 , 0.28835E-6 , 0.12133E-7,
  31      +         -0.31104E-6 ,-0.17284E-9 , 0.14400E-7 , 0.68357E-7,
  32      +          0.73945E-12,-0.48149E-10, 0.55823E-9 ,-0.10089E-9,
  33      +         -0.10927E-5 ,-0.97897E-9 , 0.12854E-6 ,-0.45803E-5,
  34      +          0.16858E-10, 0.12013E-6 , 0.16924E-7/
  35       DATA AZ,BE/3.845,2.975/
  36 C.
  37 C.    ------------------------------------------------------------------
  38 C.
  39       Z2=Z*Z
  40       X=EMASS/E
  41       EKZ=Z2*(EK(1)+Z*(EK(2)+Z*(EK(3)+Z*EK(4))))
  42       IF(E.GT.EKZ)THEN
  43          X2=X*X
  44          S=C(1)/Z+C(2)*X+C(3)+C(4)*Z+C(5)/X+C(6)*Z2+C(7)*Z/X+C(8)/X2+
  45      +     C(9)*Z2*Z+C(10)*Z2/X+C(11)*Z/X2+C(12)/(X2*X)
  46          GO TO 50
  47       ENDIF
  48 C
  49       EL1Z=Z2*(EL1(1)+Z*(EL1(2)+Z*(EL1(3)+Z*EL1(4))))
  50       IF(E.GT.EL1Z)THEN
  51          S=C(13)/Z+C(14)*X+C(15)
  52          GO TO 50
  53       ENDIF
  54 C
  55       EL2Z=Z2*(EL2(1)+Z*(EL2(2)+Z*(EL2(3)+Z*EL2(4))))
  56       IF(E.GT.EL2Z)THEN
  57          S=C(16)/Z+C(17)*X+C(18)
  58       ELSE
  59          S=C(19)
  60       ENDIF
  61 C
  62   50  GPHSIG=S*Z**AZ*X**BE
  63       IF(GPHSIG.LT.0.)GPHSIG=0.
  64 C
  65       END