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1 *
2 * $Id$
3 *
4 * $Log$
5 * Revision 1.1.1.1  1996/03/06 15:37:34  mclareni
6 * Add geane321 source directories
7 *
8 *
9 #include "geant321/pilot.h"
10 *CMZ :  3.21/02 29/03/94  15.41.49  by  S.Giani
11 *-- Author :
12       SUBROUTINE ERLAND (STEP, Z, A, RHO, P, E, XMASS, DEDX2)
13 C.
14 C.    ******************************************************************
15 C.    *                                                                *
16 C.    *  Calculates energy straggling using Gaussian theory in a step  *
17 C.    *                                                                *
18 C.    *  Input  STEP   =  current step-length (cm)                     *
19 C.    *         Z      =  Z of the material                            *
20 C.    *         A      =  A of the material                            *
21 C.    *         RHO    =  density of the material                      *
22 C.    *         P      =  momentum of the particle                     *
23 C.    *         E      =  energy   of the particle                     *
24 C.    *         XMASS  =  mass     of the particle                     *
25 C.    *                                                                *
26 C.    *  Output DEDX2  =  mean square of the straggling in G           *
27 C.    *                                                                *
28 C.    *    ==>Called by : ERTRCH                                       *
29 C.    *       Author    E.Nagy  *********                              *
30 C.    *       Original routine : GLANDO                                *
31 C.    *                                                                *
32 C.    ******************************************************************
33 C.
34 #include "geant321/gconst.inc"
35 *
36       IF (STEP.LT.1.E-7) THEN
37          DEDX2=0.
38          RETURN
39       ENDIF
40 *
41 *     Calculate xi factor (KeV).
42       BETA   = P/E
43       GAMMA  = E/XMASS
44       XI     = (153.5*Z*STEP*RHO)/(A*BETA*BETA)
45 *
46 *     Maximum energy transfer to atomic electron (KeV).
47       ETA    = BETA*GAMMA
48       ETASQ  = ETA*ETA
49       RATIO  = EMASS/XMASS
50       F1     = 2.*EMASS*ETASQ
51       F2     = 1.+2.*RATIO*GAMMA+RATIO*RATIO
52       EMAX   = 1.E+6*F1/F2
53 *
54 *
55 * *** and now sigma**2  in GeV
56 *        gaussian
57       DEDX2  = XI*EMAX*(1.-(BETA*BETA/2.))*1.E-12
58 *
59       END