[u/mrichter/AliRoot.git] / GEANT321 / gphys / gmcoul.F

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1995/10/24 10:21:26  cernlib
* Geant
*
*
*    NEW
#include "geant321/pilot.h"
*CMZ :  3.21/02 29/03/94  15.41.22  by  S.Giani
*-- Author :
      SUBROUTINE GMCOUL(OMEGA,DIN)
C.
C.    ******************************************************************
C.    *                                                                *
C     *       Generate NSCA single scatters in small angle approxima.  *
C.    *       for a particle with parameters VECT in common /GCTRAK/   *
C.    *                                                                *
C.    *       This subroutine must be called with the correct values   *
C.    *       of the constants OMC & CHC which depend of the medium    *
C.    *                                                                *
C.    *       OMC and CHC are computed at initialisation time (GMOLI)  *
C.    *       No lateral displacement of the particle with respect     *
C.    *       the incident direction is included.                      *
C.    *       No path length correction is included                    *
C.    *                                                                *
C.    *       Output angles overwrite VECT                             *
C.    *                                                                *
C.    *    ==>Called by : GMULTS                                       *
C.    *         Author G. Lynch (LBL)  (adapted by M. Maire  1.02.90)  *
C.    *                                                                *
C.    ******************************************************************
C.
#include "geant321/gctrak.inc"
#include "geant321/gconsp.inc"
#include "geant321/gcmulo.inc"
      PARAMETER (NSCMX = 50)
      DIMENSION DIN(3),RNDM(2*NSCMX)
      PARAMETER (OMCF=1.167)
*
*     ------------------------------------------------------------------
*
* *** Compute number of scatters (Poisson distr. with mean OMEGA0)
*
      OMEGA0 = OMCF*OMEGA
      CALL GPOISS (OMEGA0,NSCA,1)
      IF (NSCA.LE.0)THEN
         DIN(1) = 0.
         DIN(2) = 0.
         DIN(3) = 1.
         RETURN
      ENDIF
      NSCA = MIN(NSCA,NSCMX)
      CALL GRNDM (RNDM,2*NSCA)
*
* *** THMIN2 is the screening angle
      THMIN2 = (CHCMOL**2)/(OMCF*OMCMOL*(VECT(7)**2))
*
      SUMX = 0.
      SUMY = 0.
      DO 12 I=1,NSCA
         THET  = SQRT(THMIN2*((1./RNDM(I)) - 1.))
         PHI   = TWOPI*RNDM(NSCA+I)
         SUMX  = SUMX + THET*COS(PHI)
         SUMY  = SUMY + THET*SIN(PHI)
   12 CONTINUE
      THETA  = SQRT(SUMX**2 + SUMY**2)
      IF(THETA.NE.0.) THEN
      COSTH  = COS(THETA)
      SINTH  = SIN(THETA)
      CSPHI  = SUMX/THETA
      SNPHI  = SUMY/THETA
*
      DIN(1) = SINTH*CSPHI
      DIN(2) = SINTH*SNPHI
      DIN(3) = COSTH
      ELSE
         DIN(1) = 0.
         DIN(2) = 0.
         DIN(3) = 1.
      ENDIF
*
      END
Commit	Line	Data
fe4da5cc	1	*
	2	* $Id$
	3	*
	4	* $Log$
	5	* Revision 1.1.1.1 1995/10/24 10:21:26 cernlib
	6	* Geant
	7	*
	8	*
	9	* NEW
	10	#include "geant321/pilot.h"
	11	*CMZ : 3.21/02 29/03/94 15.41.22 by S.Giani
	12	*-- Author :
	13	SUBROUTINE GMCOUL(OMEGA,DIN)
	14	C.
	15	C. ******************************************************************
	16	C. * *
	17	C * Generate NSCA single scatters in small angle approxima. *
	18	C. * for a particle with parameters VECT in common /GCTRAK/ *
	19	C. * *
	20	C. * This subroutine must be called with the correct values *
	21	C. * of the constants OMC & CHC which depend of the medium *
	22	C. * *
	23	C. * OMC and CHC are computed at initialisation time (GMOLI) *
	24	C. * No lateral displacement of the particle with respect *
	25	C. * the incident direction is included. *
	26	C. * No path length correction is included *
	27	C. * *
	28	C. * Output angles overwrite VECT *
	29	C. * *
	30	C. * ==>Called by : GMULTS *
	31	C. * Author G. Lynch (LBL) (adapted by M. Maire 1.02.90) *
	32	C. * *
	33	C. ******************************************************************
	34	C.
	35	#include "geant321/gctrak.inc"
	36	#include "geant321/gconsp.inc"
	37	#include "geant321/gcmulo.inc"
	38	PARAMETER (NSCMX = 50)
	39	DIMENSION DIN(3),RNDM(2*NSCMX)
	40	PARAMETER (OMCF=1.167)
	41	*
	42	* ------------------------------------------------------------------
	43	*
	44	* *** Compute number of scatters (Poisson distr. with mean OMEGA0)
	45	*
	46	OMEGA0 = OMCF*OMEGA
	47	CALL GPOISS (OMEGA0,NSCA,1)
	48	IF (NSCA.LE.0)THEN
	49	DIN(1) = 0.
	50	DIN(2) = 0.
	51	DIN(3) = 1.
	52	RETURN
	53	ENDIF
	54	NSCA = MIN(NSCA,NSCMX)
	55	CALL GRNDM (RNDM,2*NSCA)
	56	*
	57	* *** THMIN2 is the screening angle
	58	THMIN2 = (CHCMOL*2)/(OMCFOMCMOL(VECT(7)*2))
	59	*
	60	SUMX = 0.
	61	SUMY = 0.
	62	DO 12 I=1,NSCA
	63	THET = SQRT(THMIN2*((1./RNDM(I)) - 1.))
	64	PHI = TWOPI*RNDM(NSCA+I)
65	SUMX = SUMX + THET*COS(PHI)
66	SUMY = SUMY + THET*SIN(PHI)
67	12 CONTINUE
68	THETA = SQRT(SUMX2 + SUMY2)
69	IF(THETA.NE.0.) THEN
70	COSTH = COS(THETA)
71	SINTH = SIN(THETA)
72	CSPHI = SUMX/THETA
73	SNPHI = SUMY/THETA
74	*
75	DIN(1) = SINTH*CSPHI
76	DIN(2) = SINTH*SNPHI
77	DIN(3) = COSTH
78	ELSE
79	DIN(1) = 0.
80	DIN(2) = 0.
81	DIN(3) = 1.
82	ENDIF
83	*
84	END