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[u/mrichter/AliRoot.git] / GEANT321 / gphys / gbfsig.F
1 *
2 * $Id$
3 *
4 * $Log$
5 * Revision 1.1.1.1  1995/10/24 10:21:21  cernlib
6 * Geant
7 *
8 *
9 #include "geant321/pilot.h"
10 *CMZ :  3.21/02 29/03/94  15.41.21  by  S.Giani
11 *-- Author :
12       FUNCTION GBFSIG(T,C)
13 C.    ******************************************************************
14 C.    *                                                                *
15 C.    *  It calculates a weight factor for the positron discrete       *
16 C.    *       (hard) bremsstrahlung cross section                      *
17 C.    *                                                                *
18 C.    *  Input:T kinetic energy (GeV)                                  *
19 C.    *        C cut for bremsstrahlung (BCUTE)                        *
20 C.    *        ETA ratio of positron to electron brems cross section   *
21 C.    *  Output: weight factor                                         *
22 C.    *                                                                *
23 C.    *  ===>  positron sigma = Fsig * electron sigma  <===            *
24 C.    *                                                                *
25 C.    *  Author   L. Urban                                             *
26 C.    *                                                                *
27 C.    ******************************************************************
28 C.
29       ETA = GCBREM(T)
30       IF(ETA.LT.0.0001) THEN
31          F=1.E-10
32       ELSEIF(ETA.GT.0.9999) THEN
33          F=1.
34       ELSE
35 C
36          E0=C/T
37 C
38          IF(E0.GE.1.) THEN
39             F=1.E-10
40          ELSE
41             ALFA=1./ETA
42             E1=1.-E0
43             F=ETA*E1**ALFA/E1
44          ENDIF
45       ENDIF
46 C
47       GBFSIG=F
48       END