| 1 | SUBROUTINE MPOISS(AMEAN,NPRAN)
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| 2 |
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| 3 | C-----------------------------------------------------------------------
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| 4 | C M(UON COULOMB SCATTERING) POISS(ON DISTRIBUTION)
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| 5 | C
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| 6 | C GENERATES A RANDOM NUMBER POISSON DISTRIBUTED WITH MEAN VALUE AMEAN.
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| 7 | C THIS SUBROUTINE IS IN ANALOGY WITH SUBROUTINE GPOISS.
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| 8 | C (AUTHOR: L. URBAN) OF GEANT321
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| 9 | C SEE CERN PROGRAM LIBRARY LONG WRITEUP W5013.
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| 10 | C THIS SUBROUTINE IS CALLED FROM MUCOUL
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| 11 | C ARGUMENTS:
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| 12 | C AMEAN = MEAN VALUE OF RANDOM NUMBER
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| 13 | C NPRAN = RANDOM NUMBER POISSON DISTRIBUTED
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| 14 | C
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| 15 | C REDESIGN: D. HECK IK3 FZK KARLSRUHE
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| 16 | C-----------------------------------------------------------------------
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| 17 |
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| 18 | IMPLICIT NONE
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| 19 | *KEEP,CONST.
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| 20 | COMMON /CONST/ PI,PI2,OB3,TB3,ENEPER
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| 21 | DOUBLE PRECISION PI,PI2,OB3,TB3,ENEPER
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| 22 | *KEEP,RANDPA.
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| 23 | COMMON /RANDPA/ FAC,U1,U2,RD,NSEQ,ISEED,KNOR
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| 24 | DOUBLE PRECISION FAC,U1,U2
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| 25 | REAL RD(3000)
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| 26 | INTEGER ISEED(103,10),NSEQ
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| 27 | LOGICAL KNOR
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| 28 | *KEEP,RUNPAR.
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| 29 | COMMON /RUNPAR/ FIXHEI,THICK0,HILOECM,HILOELB,
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| 30 | * STEPFC,NRRUN,NSHOW,PATAPE,MONIIN,
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| 31 | * MONIOU,MDEBUG,NUCNUC,
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| 32 | * CETAPE,
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| 33 | * SHOWNO,ISHW,NOPART,NRECS,NBLKS,MAXPRT,NDEBDL,
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| 34 | * N1STTR,MDBASE,
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| 35 | * DEBDEL,DEBUG,FDECAY,FEGS,FIRSTI,FIXINC,FIXTAR,
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| 36 | * FIX1I,FMUADD,FNKG,FPRINT,FDBASE
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| 37 | * ,GHEISH,GHESIG
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| 38 | COMMON /RUNPAC/ DSN,HOST,USER
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| 39 | DOUBLE PRECISION FIXHEI,THICK0,HILOECM,HILOELB
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| 40 | REAL STEPFC
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| 41 | INTEGER NRRUN,NSHOW,PATAPE,MONIIN,MONIOU,MDEBUG,NUCNUC,
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| 42 | * SHOWNO,ISHW,NOPART,NRECS,NBLKS,MAXPRT,NDEBDL,
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| 43 | * N1STTR,MDBASE
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| 44 | INTEGER CETAPE
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| 45 | CHARACTER*79 DSN
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| 46 | CHARACTER*20 HOST,USER
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| 47 |
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| 48 | LOGICAL DEBDEL,DEBUG,FDECAY,FEGS,FIRSTI,FIXINC,FIXTAR,
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| 49 | * FIX1I,FMUADD,FNKG,FPRINT,FDBASE
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| 50 | * ,GHEISH,GHESIG
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| 51 | *KEND.
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| 52 |
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| 53 | DOUBLE PRECISION AMEAN,AN,HMXINT,P,PLIM,RR,S,X
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| 54 | INTEGER NPRAN
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| 55 | DATA PLIM/16.D0/,HMXINT/2.D9/
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| 56 | C-----------------------------------------------------------------------
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| 57 |
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| 58 | C PROTECTION AGAINST NEGATIVE MEAN VALUES
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| 59 | AN = 0.D0
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| 60 | IF ( AMEAN .GT. 0.D0 ) THEN
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| 61 | IF ( AMEAN .LE. PLIM ) THEN
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| 62 | CALL RMMAR(RD,1,1)
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| 63 | P = EXP(-AMEAN)
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| 64 | S = P
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| 65 | IF ( RD(1) .LE. S ) GOTO 20
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| 66 | 10 AN = AN + 1.D0
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| 67 | P = P * AMEAN / AN
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| 68 | S = S + P
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| 69 | IF ( S .LT. RD(1) .AND. P .GT. 1.D-30 ) GOTO 10
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| 70 | ELSE
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| 71 | CALL RMMAR(RD,2,1)
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| 72 | RR = SQRT( -2.D0*LOG(RD(1)) )
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| 73 | X = RR * COS( PI2 * RD(2) )
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| 74 | AN = MIN( MAX( AMEAN+X*SQRT(AMEAN), 0.D0 ), HMXINT )
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| 75 | ENDIF
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| 76 | ENDIF
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| 77 | 20 NPRAN = AN
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| 78 |
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| 79 | RETURN
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| 80 | END
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