pythia/pyinki.F

   1
   2 C*********************************************************************
   3
   4       SUBROUTINE PYINKI(MODKI)
   5
   6 C...Sets up kinematics, including rotations and boosts to/from CM frame.
   7       COMMON/LUJETS/N,K(4000,5),P(4000,5),V(4000,5)
   8       COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
   9       COMMON/LUDAT2/KCHG(500,3),PMAS(500,4),PARF(2000),VCKM(4,4)
  10       COMMON/PYSUBS/MSEL,MSUB(200),KFIN(2,-40:40),CKIN(200)
  11       COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
  12       COMMON/PYINT1/MINT(400),VINT(400)
  13       SAVE /LUJETS/,/LUDAT1/,/LUDAT2/
  14       SAVE /PYSUBS/,/PYPARS/,/PYINT1/
  15
  16 C...Set initial flavour state.
  17       N=2
  18       DO 100 I=1,2
  19       K(I,1)=1
  20       K(I,2)=MINT(10+I)
  21   100 CONTINUE
  22
  23 C...Reset boost. Do kinematics for various cases.
  24       DO 110 J=6,10
  25       VINT(J)=0.
  26   110 CONTINUE
  27
  28 C...Set up kinematics for events defined in CM frame.
  29       IF(MINT(111).EQ.1) THEN
  30         WIN=VINT(290)
  31         IF(MODKI.EQ.1) WIN=PARP(171)*VINT(290)
  32         S=WIN**2
  33         P(1,5)=VINT(3)
  34         P(2,5)=VINT(4)
  35         P(1,1)=0.
  36         P(1,2)=0.
  37         P(2,1)=0.
  38         P(2,2)=0.
  39         P(1,3)=SQRT(((S-P(1,5)**2-P(2,5)**2)**2-(2.*P(1,5)*P(2,5))**2)/
  40      &  (4.*S))
  41         P(2,3)=-P(1,3)
  42         P(1,4)=SQRT(P(1,3)**2+P(1,5)**2)
  43         P(2,4)=SQRT(P(2,3)**2+P(2,5)**2)
  44
  45 C...Set up kinematics for fixed target events.
  46       ELSEIF(MINT(111).EQ.2) THEN
  47         WIN=VINT(290)
  48         IF(MODKI.EQ.1) WIN=PARP(171)*VINT(290)
  49         P(1,5)=VINT(3)
  50         P(2,5)=VINT(4)
  51         P(1,1)=0.
  52         P(1,2)=0.
  53         P(2,1)=0.
  54         P(2,2)=0.
  55         P(1,3)=WIN
  56         P(1,4)=SQRT(P(1,3)**2+P(1,5)**2)
  57         P(2,3)=0.
  58         P(2,4)=P(2,5)
  59         S=P(1,5)**2+P(2,5)**2+2.*P(2,4)*P(1,4)
  60         VINT(10)=P(1,3)/(P(1,4)+P(2,4))
  61         CALL LUROBO(0.,0.,0.,0.,-VINT(10))
  62
  63 C...Set up kinematics for events in user-defined frame.
  64       ELSEIF(MINT(111).EQ.3) THEN
  65         P(1,5)=VINT(3)
  66         P(2,5)=VINT(4)
  67         P(1,4)=SQRT(P(1,1)**2+P(1,2)**2+P(1,3)**2+P(1,5)**2)
  68         P(2,4)=SQRT(P(2,1)**2+P(2,2)**2+P(2,3)**2+P(2,5)**2)
  69         DO 120 J=1,3
  70         VINT(7+J)=(DBLE(P(1,J))+DBLE(P(2,J)))/DBLE(P(1,4)+P(2,4))
  71   120   CONTINUE
  72         CALL LUROBO(0.,0.,-VINT(8),-VINT(9),-VINT(10))
  73         VINT(7)=ULANGL(P(1,1),P(1,2))
  74         CALL LUROBO(0.,-VINT(7),0.,0.,0.)
  75         VINT(6)=ULANGL(P(1,3),P(1,1))
  76         CALL LUROBO(-VINT(6),0.,0.,0.,0.)
  77         S=P(1,5)**2+P(2,5)**2+2.*(P(1,4)*P(2,4)-P(1,3)*P(2,3))
  78
  79 C...Set up kinematics for events with user-defined four-vectors.
  80       ELSEIF(MINT(111).EQ.4) THEN
  81         PMS1=P(1,4)**2-P(1,1)**2-P(1,2)**2-P(1,3)**2
  82         P(1,5)=SIGN(SQRT(ABS(PMS1)),PMS1)
  83         PMS2=P(2,4)**2-P(2,1)**2-P(2,2)**2-P(2,3)**2
  84         P(2,5)=SIGN(SQRT(ABS(PMS2)),PMS2)
  85         DO 130 J=1,3
  86         VINT(7+J)=(DBLE(P(1,J))+DBLE(P(2,J)))/DBLE(P(1,4)+P(2,4))
  87   130   CONTINUE
  88         CALL LUROBO(0.,0.,-VINT(8),-VINT(9),-VINT(10))
  89         VINT(7)=ULANGL(P(1,1),P(1,2))
  90         CALL LUROBO(0.,-VINT(7),0.,0.,0.)
  91         VINT(6)=ULANGL(P(1,3),P(1,1))
  92         CALL LUROBO(-VINT(6),0.,0.,0.,0.)
  93         S=(P(1,4)+P(2,4))**2
  94
  95 C...Set up kinematics for events with user-defined five-vectors.
  96       ELSEIF(MINT(111).EQ.5) THEN
  97         DO 140 J=1,3
  98         VINT(7+J)=(DBLE(P(1,J))+DBLE(P(2,J)))/DBLE(P(1,4)+P(2,4))
  99   140   CONTINUE
 100         CALL LUROBO(0.,0.,-VINT(8),-VINT(9),-VINT(10))
 101         VINT(7)=ULANGL(P(1,1),P(1,2))
 102         CALL LUROBO(0.,-VINT(7),0.,0.,0.)
 103         VINT(6)=ULANGL(P(1,3),P(1,1))
 104         CALL LUROBO(-VINT(6),0.,0.,0.,0.)
 105         S=(P(1,4)+P(2,4))**2
 106       ENDIF
 107
 108 C...Return or error for too low CM energy.
 109       IF(MODKI.EQ.1.AND.S.LT.PARP(2)**2) THEN
 110         IF(MSTP(172).LE.1) THEN
 111           CALL LUERRM(23,
 112      &    '(PYINKI:) too low invariant mass in this event')
 113         ELSE
 114           MSTI(61)=1
 115           RETURN
 116         ENDIF
 117       ENDIF
 118
 119 C...Save information on incoming particles.
 120       VINT(1)=SQRT(S)
 121       VINT(2)=S
 122       IF(MINT(111).GE.4) VINT(3)=P(1,5)
 123       IF(MINT(111).GE.4) VINT(4)=P(2,5)
 124       VINT(5)=P(1,3)
 125       IF(MODKI.EQ.0) VINT(289)=S
 126       DO 150 J=1,5
 127       V(1,J)=0.
 128       V(2,J)=0.
 129       VINT(290+J)=P(1,J)
 130       VINT(295+J)=P(2,J)
 131   150 CONTINUE
 132
 133 C...Store pT cut-off and related constants to be used in generation.
 134       IF(MODKI.EQ.0) VINT(285)=CKIN(3)
 135       IF(MSTP(82).LE.1) THEN
 136         IF(MINT(121).GT.1) PARP(81)=1.30+0.15*LOG(VINT(1)/200.)/
 137      &  LOG(900./200.)
 138         PTMN=PARP(81)
 139       ELSE
 140         IF(MINT(121).GT.1) PARP(82)=1.25+0.15*LOG(VINT(1)/200.)/
 141      &  LOG(900./200.)
 142         PTMN=PARP(82)
 143       ENDIF
 144       VINT(149)=4.*PTMN**2/S
 145
 146       RETURN
 147       END