GEANT321/gphys/gphsg1.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:21:29  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 GPHSG1(E)
  13 C.
  14 C.    ******************************************************************
  15 C.    *                                                                *
  16 C.    *       FUNCTION TO COMPUTE THE PHOTOEFFECT TOTAL CROSS-SECTION  *
  17 C.    *       AS A FUNCTION OF E                                       *
  18 C.    *                                                                *
  19 C.    *    ==>CALLED BY : GPHOTI                                       *
  20 C.    *                                                                *
  21 C.    *    (1) Sandia parametrizsation is used;                        *
  22 C.    *    (2) GPHSG1 in cm**2/g.                                      *
  23 C.    *    (3) E in GeV                                                *
  24 C.    *                                                                *
  25 C.    *     J. Chwastowski 17.11.92                                    *
  26 C.    ******************************************************************
  27 C.
  28 #include "geant321/gcbank.inc"
  29 #include "geant321/gcjloc.inc"
  30 #include "geant321/gconsp.inc"
  31 #include "geant321/gc10ev.inc"
  32 #if !defined(CERNLIB_SINGLE)
  33       DOUBLE PRECISION EINV,ECUR,ONE
  34 #endif
  35       PARAMETER (ONE=1)
  36 C.
  37 C.    ------------------------------------------------------------------
  38 C.
  39       RES = 0.
  40       IF(E.LT.G10EV) GO TO 20
  41 C Use Sandia data
  42       JPHXS = LQ(JPHOT-1)
  43       IPOINT = JPHXS+Q(JPHXS+1)*3+2
  44       IMAX = Q(IPOINT)
  45       IPOINT = IPOINT+1
  46       ECUR = E*1.E6
  47       IF(ECUR.LT.Q(IPOINT)) GO TO 20
  48       EINV = ONE/ECUR
  49       DO 10 I = 2,IMAX
  50          IPOINT = IPOINT+5
  51          IF(ECUR.LT.Q(IPOINT)) THEN
  52             J = IPOINT+1
  53             RES = EINV*(Q(J)+EINV*(Q(J+1)+EINV*(Q(J+2)+EINV*Q(J+3))))
  54             GO TO 20
  55          ENDIF
  56    10 CONTINUE
  57 C This value is in cm**2/g
  58    20 GPHSG1 = MAX(RES,0.)
  59 C
  60       END