PYTHIA/pythia/pyspli.F

   1
   2 C*********************************************************************
   3
   4       SUBROUTINE PYSPLI(KF,KFLIN,KFLCH,KFLSP)
   5
   6 C...In case of a hadron remnant which is more complicated than just a
   7 C...quark or a diquark, split it into two (partons or hadron + parton).
   8       COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
   9       COMMON/PYINT1/MINT(400),VINT(400)
  10       SAVE /PYPARS/,/PYINT1/
  11       DIMENSION KFL(3)
  12
  13 C...Preliminaries. Parton composition.
  14       KFA=IABS(KF)
  15       KFS=ISIGN(1,KF)
  16       KFL(1)=MOD(KFA/1000,10)
  17       KFL(2)=MOD(KFA/100,10)
  18       KFL(3)=MOD(KFA/10,10)
  19       IF(KFA.EQ.22.AND.MINT(109).EQ.2) THEN
  20         KFL(2)=INT(1.5+RLU(0))
  21         IF(MINT(105).EQ.333) KFL(2)=3
  22         IF(MINT(105).EQ.443) KFL(2)=4
  23         KFL(3)=KFL(2)
  24       ELSEIF((KFA.EQ.111.OR.KFA.EQ.113).AND.RLU(0).GT.0.5) THEN
  25         KFL(2)=2
  26         KFL(3)=2
  27       ELSEIF(KFA.EQ.223.AND.RLU(0).GT.0.5) THEN
  28         KFL(2)=1
  29         KFL(3)=1
  30       ENDIF
  31       IF(KFLIN.NE.21.AND.KFLIN.NE.22.AND.KFLIN.NE.23) THEN
  32         KFLR=KFLIN*KFS
  33       ELSE
  34         KFLR=KFLIN
  35       ENDIF
  36       KFLCH=0
  37
  38 C...Subdivide lepton.
  39       IF(KFA.GE.11.AND.KFA.LE.18) THEN
  40         IF(KFLR.EQ.KFA) THEN
  41           KFLSP=KFS*22
  42         ELSEIF(KFLR.EQ.22) THEN
  43           KFLSP=KFA
  44         ELSEIF(KFLR.EQ.-24.AND.MOD(KFA,2).EQ.1) THEN
  45           KFLSP=KFA+1
  46         ELSEIF(KFLR.EQ.24.AND.MOD(KFA,2).EQ.0) THEN
  47           KFLSP=KFA-1
  48         ELSEIF(KFLR.EQ.21) THEN
  49           KFLSP=KFA
  50           KFLCH=KFS*21
  51         ELSE
  52           KFLSP=KFA
  53           KFLCH=-KFLR
  54         ENDIF
  55
  56 C...Subdivide photon.
  57       ELSEIF(KFA.EQ.22.AND.MINT(109).NE.2) THEN
  58         IF(KFLR.NE.21) THEN
  59           KFLSP=-KFLR
  60         ELSE
  61           RAGR=0.75*RLU(0)
  62           KFLSP=1
  63           IF(RAGR.GT.0.125) KFLSP=2
  64           IF(RAGR.GT.0.625) KFLSP=3
  65           IF(RLU(0).GT.0.5) KFLSP=-KFLSP
  66           KFLCH=-KFLSP
  67         ENDIF
  68
  69 C...Subdivide Reggeon or Pomeron.
  70       ELSEIF(KFA.EQ.28.OR.KFA.EQ.29) THEN
  71         IF(KFLIN.EQ.21) THEN
  72           KFLSP=KFS*21
  73         ELSE
  74           KFLSP=-KFLIN
  75         ENDIF
  76
  77 C...Subdivide meson.
  78       ELSEIF(KFL(1).EQ.0) THEN
  79         KFL(2)=KFL(2)*(-1)**KFL(2)
  80         KFL(3)=-KFL(3)*(-1)**IABS(KFL(2))
  81         IF(KFLR.EQ.KFL(2)) THEN
  82           KFLSP=KFL(3)
  83         ELSEIF(KFLR.EQ.KFL(3)) THEN
  84           KFLSP=KFL(2)
  85         ELSEIF(KFLR.EQ.21.AND.RLU(0).GT.0.5) THEN
  86           KFLSP=KFL(2)
  87           KFLCH=KFL(3)
  88         ELSEIF(KFLR.EQ.21) THEN
  89           KFLSP=KFL(3)
  90           KFLCH=KFL(2)
  91         ELSEIF(KFLR*KFL(2).GT.0) THEN
  92           CALL LUKFDI(-KFLR,KFL(2),KFDUMP,KFLCH)
  93           KFLSP=KFL(3)
  94         ELSE
  95           CALL LUKFDI(-KFLR,KFL(3),KFDUMP,KFLCH)
  96           KFLSP=KFL(2)
  97         ENDIF
  98
  99 C...Subdivide baryon.
 100       ELSE
 101         NAGR=0
 102         DO 100 J=1,3
 103         IF(KFLR.EQ.KFL(J)) NAGR=NAGR+1
 104   100   CONTINUE
 105         IF(NAGR.GE.1) THEN
 106           RAGR=0.00001+(NAGR-0.00002)*RLU(0)
 107           IAGR=0
 108           DO 110 J=1,3
 109           IF(KFLR.EQ.KFL(J)) RAGR=RAGR-1.
 110           IF(IAGR.EQ.0.AND.RAGR.LE.0.) IAGR=J
 111   110     CONTINUE
 112         ELSE
 113           IAGR=1.00001+2.99998*RLU(0)
 114         ENDIF
 115         ID1=1
 116         IF(IAGR.EQ.1) ID1=2
 117         IF(IAGR.EQ.1.AND.KFL(3).GT.KFL(2)) ID1=3
 118         ID2=6-IAGR-ID1
 119         KSP=3
 120         IF(MOD(KFA,10).EQ.2.AND.KFL(1).EQ.KFL(2)) THEN
 121           IF(IAGR.NE.3.AND.RLU(0).GT.0.25) KSP=1
 122         ELSEIF(MOD(KFA,10).EQ.2.AND.KFL(2).GE.KFL(3)) THEN
 123           IF(IAGR.NE.1.AND.RLU(0).GT.0.25) KSP=1
 124         ELSEIF(MOD(KFA,10).EQ.2) THEN
 125           IF(IAGR.EQ.1) KSP=1
 126           IF(IAGR.NE.1.AND.RLU(0).GT.0.75) KSP=1
 127         ENDIF
 128         KFLSP=1000*KFL(ID1)+100*KFL(ID2)+KSP
 129         IF(KFLR.EQ.21) THEN
 130           KFLCH=KFL(IAGR)
 131         ELSEIF(NAGR.EQ.0.AND.KFLR.GT.0) THEN
 132           CALL LUKFDI(-KFLR,KFL(IAGR),KFDUMP,KFLCH)
 133         ELSEIF(NAGR.EQ.0) THEN
 134           CALL LUKFDI(10000+KFLSP,-KFLR,KFDUMP,KFLCH)
 135           KFLSP=KFL(IAGR)
 136         ENDIF
 137       ENDIF
 138
 139 C...Add on correct sign for result.
 140       KFLCH=KFLCH*KFS
 141       KFLSP=KFLSP*KFS
 142
 143       RETURN
 144       END