| 1 | SUBROUTINE DIFRAC( NRETFL )
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| 2 |
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| 3 | C-----------------------------------------------------------------------
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| 4 | C (SINGLE) DIF(F)RAC(TION)
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| 5 | C
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| 6 | C SETS PARAMETERS FOR HDPM IN CASE OF SINGLE DIFFRACTION
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| 7 | C THIS SUBROUTINE IS CALLED FROM HDPM
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| 8 | C ARGUMENT:
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| 9 | C NRETFL = 0 CORRECT ENDING OF SUBROUTINE
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| 10 | C = 1 INCORRECT ENDING OF SUBROUTINE
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| 11 | C-----------------------------------------------------------------------
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| 12 |
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| 13 | IMPLICIT DOUBLE PRECISION (A-H,O-Z)
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| 14 | *KEEP,DPMFLG.
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| 15 | COMMON /DPMFLG/ NFLAIN,NFLDIF,NFLPI0,NFLCHE,NFLPIF,NFRAGM
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| 16 | INTEGER NFLAIN,NFLDIF,NFLPI0,NFLCHE,NFLPIF,NFRAGM
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| 17 | *KEEP,INTER.
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| 18 | COMMON /INTER/ AVCH,AVCH3,DC0,DLOG,DMLOG,ECMDIF,ECMDPM,ELAB,
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| 19 | * FNEUT,FNEUT2,GNU,PLAB,POSC2,POSC3,POSN2,POSN3,
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| 20 | * RC3TO2,S,SEUGF,SEUGP,SLOG,SLOGSQ,SMLOG,
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| 21 | * WIDC2,WIDC3,WIDN2,WIDN3,YCM,YY0,ZN,
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| 22 | * IDIF,ITAR
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| 23 | DOUBLE PRECISION AVCH,AVCH3,DC0,DLOG,DMLOG,ECMDIF,ECMDPM,ELAB,
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| 24 | * FNEUT,FNEUT2,GNU,PLAB,POSC2,POSC3,POSN2,POSN3,
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| 25 | * RC3TO2,S,SEUGF,SEUGP,SLOG,SLOGSQ,SMLOG,
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| 26 | * WIDC2,WIDC3,WIDN2,WIDN3,YCM,YY0,ZN
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| 27 | INTEGER IDIF,ITAR
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| 28 | *KEEP,LEPAR.
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| 29 | COMMON /LEPAR/ LEPAR1,LEPAR2,LASTPI,NRESPC,NRESPN,NCPLUS
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| 30 | INTEGER LEPAR1,LEPAR2,LASTPI,NRESPC,NRESPN,NCPLUS
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| 31 | *KEEP,PAM.
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| 32 | COMMON /PAM/ PAMA,SIGNUM
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| 33 | DOUBLE PRECISION PAMA(6000),SIGNUM(6000)
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| 34 | *KEEP,PARPAR.
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| 35 | COMMON /PARPAR/ CURPAR,SECPAR,PRMPAR,OUTPAR,C,
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| 36 | * E00,E00PN,PTOT0,PTOT0N,THICKH,ITYPE,LEVL
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| 37 | DOUBLE PRECISION CURPAR(14),SECPAR(14),PRMPAR(14),OUTPAR(14),
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| 38 | * C(50),E00,E00PN,PTOT0,PTOT0N,THICKH
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| 39 | INTEGER ITYPE,LEVL
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| 40 | *KEEP,PARPAE.
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| 41 | DOUBLE PRECISION GAMMA,COSTHE,PHI,H,T,X,Y,CHI,BETA,GCM,ECM
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| 42 | EQUIVALENCE (CURPAR(2),GAMMA), (CURPAR(3),COSTHE),
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| 43 | * (CURPAR(4), PHI ), (CURPAR(5), H ),
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| 44 | * (CURPAR(6), T ), (CURPAR(7), X ),
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| 45 | * (CURPAR(8), Y ), (CURPAR(9), CHI ),
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| 46 | * (CURPAR(10),BETA), (CURPAR(11),GCM ),
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| 47 | * (CURPAR(12),ECM )
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| 48 | *KEEP,RANDPA.
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| 49 | COMMON /RANDPA/ FAC,U1,U2,RD,NSEQ,ISEED,KNOR
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| 50 | DOUBLE PRECISION FAC,U1,U2
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| 51 | REAL RD(3000)
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| 52 | INTEGER ISEED(103,10),NSEQ
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| 53 | LOGICAL KNOR
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| 54 | *KEEP,REST.
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| 55 | COMMON /REST/ CONTNE,TAR,LT
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| 56 | DOUBLE PRECISION CONTNE(3),TAR
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| 57 | INTEGER LT
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| 58 | *KEEP,RUNPAR.
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| 59 | COMMON /RUNPAR/ FIXHEI,THICK0,HILOECM,HILOELB,
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| 60 | * STEPFC,NRRUN,NSHOW,PATAPE,MONIIN,
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| 61 | * MONIOU,MDEBUG,NUCNUC,
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| 62 | * CETAPE,
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| 63 | * SHOWNO,ISHW,NOPART,NRECS,NBLKS,MAXPRT,NDEBDL,
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| 64 | * N1STTR,MDBASE,
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| 65 | * DEBDEL,DEBUG,FDECAY,FEGS,FIRSTI,FIXINC,FIXTAR,
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| 66 | * FIX1I,FMUADD,FNKG,FPRINT,FDBASE
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| 67 | * ,GHEISH,GHESIG
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| 68 | COMMON /RUNPAC/ DSN,HOST,USER
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| 69 | DOUBLE PRECISION FIXHEI,THICK0,HILOECM,HILOELB
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| 70 | REAL STEPFC
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| 71 | INTEGER NRRUN,NSHOW,PATAPE,MONIIN,MONIOU,MDEBUG,NUCNUC,
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| 72 | * SHOWNO,ISHW,NOPART,NRECS,NBLKS,MAXPRT,NDEBDL,
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| 73 | * N1STTR,MDBASE
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| 74 | INTEGER CETAPE
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| 75 | CHARACTER*79 DSN
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| 76 | CHARACTER*20 HOST,USER
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| 77 |
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| 78 | LOGICAL DEBDEL,DEBUG,FDECAY,FEGS,FIRSTI,FIXINC,FIXTAR,
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| 79 | * FIX1I,FMUADD,FNKG,FPRINT,FDBASE
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| 80 | * ,GHEISH,GHESIG
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| 81 | *KEND.
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| 82 |
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| 83 | C-----------------------------------------------------------------------
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| 84 |
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| 85 | IF ( DEBUG ) WRITE(MDEBUG,*) 'DIFRAC:'
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| 86 |
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| 87 | C DECIDE FIRST, WHETHER PROJECTILE OR TARGET DIFFRACTION
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| 88 | CALL RMMAR( RD,1,1 )
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| 89 | IF ( RD(1) .LE. 0.5 ) THEN
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| 90 | C PROJECTILE DIFFRACTON, TARGET DIFFRACTION FLAG IS NOT SET
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| 91 | NFTARD = 0
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| 92 | C MASS OF INCOMING PARTICLE AND PI(0) MASS
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| 93 | C PI(0) IS MINIMAL OUTCOME OF SECONDARIES IN DIFRAC
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| 94 | XM0 = ( PAMA(LEPAR1) + PAMA(7) )**2
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| 95 | ELSE
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| 96 | C TARGET DIFFRACTON, SET TARGET DIFFRACTION FLAG
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| 97 | NFTARD = 1
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| 98 | C MASS OF NUCLEON AND PI(0) MASS
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| 99 | C PI(0) IS MINIMAL OUTCOME OF SECONDARIES IN DIFRAC
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| 100 | XM0 = ( PAMA(LEPAR2) + PAMA(7) )**2
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| 101 | ENDIF
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| 102 | C MAXIMAL DIFFRACTIVE MASS, FACTOR 0.15 GIVEN BY COHERENCE CONDITION
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| 103 | XMX = 0.15D0 * S
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| 104 |
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| 105 | C THROW MAXIMAL 200 TIMES TO GET A GOOD DIFFRACTIVE MASS
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| 106 | NCDIFL = 0
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| 107 | 7 CONTINUE
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| 108 | C GET DIFFRACTIVE MASS
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| 109 | CALL RMMAR( RD,2,1 )
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| 110 | C GET S (=ECM**2) (WHY THIS WAY OF THROWING ???)
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| 111 | SDIF = (XMX/XM0)**RD(1) * XM0
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| 112 |
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| 113 | IF ( SDIF .LE. XM0 ) THEN
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| 114 | IF ( NCDIFL .LE. 200 ) THEN
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| 115 | NCDIFL = NCDIFL + 1
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| 116 | GOTO 7
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| 117 | ELSE
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| 118 | C SET RETURN FLAG TO ERROR
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| 119 | NRETFL = 1
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| 120 | RETURN
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| 121 | ENDIF
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| 122 | ENDIF
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| 123 |
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| 124 | C DISTRIBUTION OF DIFFRACTIVE MASS FLATTENS OFF FOR DIFFRACTIVE
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| 125 | C MASS SQUARED .LE. 2 GEV
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| 126 | IF ( SDIF .LE. 2.D0 ) THEN
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| 127 | C----- SO GEHT DAS NICHT!! 16.12.91 D.H.
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| 128 | SDIF = RD(2) * (2.D0 - XM0) + XM0
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| 129 | ENDIF
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| 130 | C SQRT(S) IS ECM
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| 131 | ECMDIF = SQRT(SDIF)
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| 132 | C LOG(S), LOG(S)**2
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| 133 | DLOG = LOG(SDIF)
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| 134 | DLOGSQ = DLOG**2
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| 135 | IF ( DEBUG ) WRITE(MDEBUG,*) 'DIFRAC: SDIF,ECMDIF,NFTARD=',
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| 136 | * SNGL(SDIF),SNGL(ECMDIF),NFTARD
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| 137 |
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| 138 | C RAPIDITY IN CMS OF DIFFRACTIVE SYSTEM
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| 139 | C TO CALCULATE DMLOG, SUBTRACT SUM OF MASS SQUARES FROM SDIF
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| 140 | C PI(0) MASS SQUARED IS 0.0182.
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| 141 | IF ( NFTARD .EQ. 0 ) THEN
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| 142 | YY0 = LOG(ECMDPM/ECMDIF)
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| 143 | DMLOG = LOG(SDIF - 0.0182D0 - PAMA(LEPAR1)**2)
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| 144 | ELSE
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| 145 | YY0 = -LOG(ECMDPM/ECMDIF)
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| 146 | DMLOG = LOG(SDIF - 0.0182D0 - PAMA(LEPAR2)**2)
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| 147 | ENDIF
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| 148 | IF ( DEBUG ) WRITE(MDEBUG,*) 'DIFRAC: YY0,DMLOG=',
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| 149 | * SNGL(YY0),SNGL(DMLOG)
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| 150 | C CENTRAL RAPIDITY DENSITY IN CMS OF DIFFRACTIVE SYSTEM
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| 151 | C PARAMETRISATION SEE CAPDEVIELLE,J.PHYS.G:NUCL.PHYS.16(1990)1539 EQ.7
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| 152 | C WE USE ONLY THE LOW-ENERGY PART OF THE PARAMETRISATION, AS SDIF DOES
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| 153 | C NOT REACH THE HIGHER VALUES
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| 154 | DC0 = 0.82D0 * (SDIF**0.107D0)
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| 155 |
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| 156 | C THERE ARE 3 ENERGY DEPENDENT FORMULAS FOR AVERAGE CHARGED
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| 157 | C MULTIPLICITY ( AVCH1 );
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| 158 | C PARAMETRISATIONS SEE CAPDEVIELLE,J.PHYS.G:NUCL.PHYS.16(1990)1539 EQ.8
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| 159 | IF ( ECMDIF .LE. 187.5D0 ) THEN
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| 160 | C CHARGED MULTIPLICITY (M**2 IN PLACE OF S)
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| 161 | AVCH1 = 0.57D0 + 0.584D0*DLOG + 0.127D0*DLOGSQ
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| 162 | ELSEIF ( ECMDIF .LE. 945.5D0 ) THEN
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| 163 | AVCH1 = -6.55D0 + 6.89D0 * SDIF**0.131D0
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| 164 | ELSE
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| 165 | AVCH1 = 3.4D0 * SDIF**0.17D0
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| 166 | ENDIF
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| 167 | C PARAMETRISATION IS BASED ON COLLIDER DATA WHERE PROTON AND ANTIPROTON
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| 168 | C ARE INCLUDED. LOWER LIMIT FOR AVERAGE CHARGED MULTIPLICITY IS 1.
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| 169 | AVCH1 = MAX( 1.D0, AVCH1 )
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| 170 |
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| 171 | C CENTER OF GAUSSIAN 1ST+2ND STRING OF FRAGMENTATION SYSTEM
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| 172 | POSC2 = 0.146D0 * DMLOG + 0.072D0
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| 173 | C WIDTH OF GAUSSIAN 1ST+2ND STRING OF FRAGMENTATION SYSTEM
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| 174 | WIDC2 = 0.120D0 * DMLOG + 0.180D0
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| 175 | C INTERACTION FACTOR GNU FOR INTERACTION WITH NUCLEUS;
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| 176 | IF ( NFLAIN .EQ. 0 ) THEN
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| 177 | GNU = 1.D0
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| 178 | AVCH3 = 0.D0
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| 179 | POSC3 = 0.D0
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| 180 | WIDC3 = 1.D0
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| 181 | ELSE
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| 182 | C NEW PARAMETRIZATION OF J.N.CAPDEVIELLE (MARCH 93)
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| 183 | GNU = (0.4826D0 + 3.522D-2 * DLOG) * TAR**0.31D0
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| 184 | C CENTER OF GAUSSIAN FOR 3RD STRING (FROM TARGET)
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| 185 | POSC3 = +3.D0 - 2.575D0 * EXP( -0.081756452D0 * GNU )
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| 186 | C WIDTH OF GAUSSIAN FOR 3RD STRING (FROM TARGET)
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| 187 | WIDC3 = 1.2338466D0 + 0.078969916D0 * LOG(GNU)
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| 188 | IF ( ECMDIF .LE. 137.D0 ) THEN
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| 189 | AVCH3 = 0.57D0 * AVCH1 * (GNU-1.D0)
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| 190 | ELSE
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| 191 | AVCH3 = 0.5D0 * AVCH1 * (GNU-1.D0)
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| 192 | ENDIF
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| 193 | ENDIF
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| 194 | IF ( DEBUG ) WRITE(MDEBUG,100)
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| 195 | * SNGL(POSC2),SNGL(WIDC2),SNGL(POSC3),SNGL(WIDC3)
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| 196 | 100 FORMAT(' DIFRAC: POSC2,WIDC2,POSC3,WIDC3=',4F12.7)
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| 197 | C AVERAGE CHARGED, INCLUDING THOSE FROM TARGET
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| 198 | AVCH = AVCH1 + AVCH3
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| 199 | C THE FOLOWING PROCEDURE IS TO PRODUCE PHOTONS FROM UNKNOWN NEUTRAL
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| 200 | C DECAYS FOLLOWING CORRELATION WITH CHARGED PARTICLES BASED ON
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| 201 | C PHOTON EXCESS AT COLLIDER EXPERIMENTS. SEUGP IS <N_PHOTON>
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| 202 | C PROBLEM OF THE RISE OF THE UNKNOWN ETA PRODUCTION CROSS SECTION
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| 203 | C IS SOLVED WITH PARAMETRISATION OF UA5 (Z. PHYS. C43 (1989) 75)
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| 204 | IF ( ECMDIF .LE. 103.D0 ) THEN
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| 205 | SEUGP = -1.27D0 + 0.52D0 * DLOG + 0.148D0 * DLOGSQ
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| 206 | ELSE
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| 207 | C AT HIGH DIFFRACTIVE MASS USE PARAMETRISATION OF THOUW ????
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| 208 | SEUGP = -18.7D0 + 11.55D0 * SDIF**0.1195D0
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| 209 | ENDIF
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| 210 | SEUGP = MAX( 0.5D0, SEUGP )
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| 211 | IF ( DEBUG ) WRITE(MDEBUG,110)
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| 212 | * SNGL(DC0),SNGL(AVCH1),SNGL(AVCH3),SNGL(AVCH),SNGL(SEUGP)
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| 213 | 110 FORMAT(' DIFRAC: DC0,AVCH1,AVCH3,AVCH,SEUGP=',5F12.6)
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| 214 |
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| 215 | C SET RETURN FLAG TO OK
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| 216 | NRETFL = 0
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| 217 | RETURN
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| 218 | END
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