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fe4da5cc | 1 | * |
2 | * $Id$ | |
3 | * | |
4 | * $Log$ | |
5 | * Revision 1.1.1.1 1995/10/24 10:21:23 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 | SUBROUTINE GDECA2(XM0,XM1,XM2,PCM) | |
13 | C. | |
14 | C. ****************************************************************** | |
15 | C. * * | |
16 | C. * Simulates two body decay process with isotropic angular * | |
17 | C. * distribution in CMS. * | |
18 | C. * * | |
19 | C. * ==>Called by : GDECAY * | |
20 | C. * Author G.Patrick ********* * | |
21 | C. * * | |
22 | C. ****************************************************************** | |
23 | C. | |
24 | #include "geant321/gconsp.inc" | |
25 | DIMENSION PCM(4,2) | |
26 | DIMENSION RNDM(2) | |
27 | C. | |
28 | C. ------------------------------------------------------------------ | |
29 | C. | |
30 | C Generate first decay product in CMS. | |
31 | C | |
32 | E1=(XM0*XM0+XM1*XM1-XM2*XM2)/(2.*XM0) | |
33 | P1=SQRT(ABS((E1-XM1)*(E1+XM1))) | |
34 | C | |
35 | C Isotropic decay angular distribution. | |
36 | C | |
37 | CALL GRNDM(RNDM,2) | |
38 | COSTH=2.*RNDM(1)-1. | |
39 | IF(ABS(COSTH).GE.1.0) THEN | |
40 | COSTH=SIGN(1.,COSTH) | |
41 | SINTH=0. | |
42 | ELSE | |
43 | SINTH=SQRT((1.-COSTH)*(1.+COSTH)) | |
44 | ENDIF | |
45 | PHI=TWOPI*RNDM(2) | |
46 | C | |
47 | C Polar co-ordinates to momentum components. | |
48 | C | |
49 | PCM(1,1)=P1*SINTH*COS(PHI) | |
50 | PCM(2,1)=P1*SINTH*SIN(PHI) | |
51 | PCM(3,1)=P1*COSTH | |
52 | PCM(4,1)=E1 | |
53 | C | |
54 | C Generate second decay product. | |
55 | C | |
56 | PCM(1,2)=-PCM(1,1) | |
57 | PCM(2,2)=-PCM(2,1) | |
58 | PCM(3,2)=-PCM(3,1) | |
59 | PCM(4,2)=SQRT(PCM(1,2)**2+PCM(2,2)**2+PCM(3,2)**2+XM2*XM2) | |
60 | C | |
61 | END |