+++ /dev/null
-
-C*********************************************************************
-
- SUBROUTINE LU3ENT(IP,KF1,KF2,KF3,PECM,X1,X3)
-
-C...Purpose: to store three partons or particles in their CM frame,
-C...with the first along the +z axis and the third in the (x,z)
-C...plane with x > 0.
- COMMON/LUJETS/N,K(4000,5),P(4000,5),V(4000,5)
- COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
- COMMON/LUDAT2/KCHG(500,3),PMAS(500,4),PARF(2000),VCKM(4,4)
- SAVE /LUJETS/,/LUDAT1/,/LUDAT2/
-
-C...Standard checks.
- MSTU(28)=0
- IF(MSTU(12).GE.1) CALL LULIST(0)
- IPA=MAX(1,IABS(IP))
- IF(IPA.GT.MSTU(4)-2) CALL LUERRM(21,
- &'(LU3ENT:) writing outside LUJETS memory')
- KC1=LUCOMP(KF1)
- KC2=LUCOMP(KF2)
- KC3=LUCOMP(KF3)
- IF(KC1.EQ.0.OR.KC2.EQ.0.OR.KC3.EQ.0) CALL LUERRM(12,
- &'(LU3ENT:) unknown flavour code')
-
-C...Find masses. Reset K, P and V vectors.
- PM1=0.
- IF(MSTU(10).EQ.1) PM1=P(IPA,5)
- IF(MSTU(10).GE.2) PM1=ULMASS(KF1)
- PM2=0.
- IF(MSTU(10).EQ.1) PM2=P(IPA+1,5)
- IF(MSTU(10).GE.2) PM2=ULMASS(KF2)
- PM3=0.
- IF(MSTU(10).EQ.1) PM3=P(IPA+2,5)
- IF(MSTU(10).GE.2) PM3=ULMASS(KF3)
- DO 110 I=IPA,IPA+2
- DO 100 J=1,5
- K(I,J)=0
- P(I,J)=0.
- V(I,J)=0.
- 100 CONTINUE
- 110 CONTINUE
-
-C...Check flavours.
- KQ1=KCHG(KC1,2)*ISIGN(1,KF1)
- KQ2=KCHG(KC2,2)*ISIGN(1,KF2)
- KQ3=KCHG(KC3,2)*ISIGN(1,KF3)
- IF(MSTU(19).EQ.1) THEN
- MSTU(19)=0
- ELSEIF(KQ1.EQ.0.AND.KQ2.EQ.0.AND.KQ3.EQ.0) THEN
- ELSEIF(KQ1.NE.0.AND.KQ2.EQ.2.AND.(KQ1+KQ3.EQ.0.OR.
- &KQ1+KQ3.EQ.4)) THEN
- ELSE
- CALL LUERRM(2,'(LU3ENT:) unphysical flavour combination')
- ENDIF
- K(IPA,2)=KF1
- K(IPA+1,2)=KF2
- K(IPA+2,2)=KF3
-
-C...Store partons/particles in K vectors for normal case.
- IF(IP.GE.0) THEN
- K(IPA,1)=1
- IF(KQ1.NE.0.AND.(KQ2.NE.0.OR.KQ3.NE.0)) K(IPA,1)=2
- K(IPA+1,1)=1
- IF(KQ2.NE.0.AND.KQ3.NE.0) K(IPA+1,1)=2
- K(IPA+2,1)=1
-
-C...Store partons in K vectors for parton shower evolution.
- ELSE
- K(IPA,1)=3
- K(IPA+1,1)=3
- K(IPA+2,1)=3
- KCS=4
- IF(KQ1.EQ.-1) KCS=5
- K(IPA,KCS)=MSTU(5)*(IPA+1)
- K(IPA,9-KCS)=MSTU(5)*(IPA+2)
- K(IPA+1,KCS)=MSTU(5)*(IPA+2)
- K(IPA+1,9-KCS)=MSTU(5)*IPA
- K(IPA+2,KCS)=MSTU(5)*IPA
- K(IPA+2,9-KCS)=MSTU(5)*(IPA+1)
- ENDIF
-
-C...Check kinematics.
- MKERR=0
- IF(0.5*X1*PECM.LE.PM1.OR.0.5*(2.-X1-X3)*PECM.LE.PM2.OR.
- &0.5*X3*PECM.LE.PM3) MKERR=1
- PA1=SQRT(MAX(1E-10,(0.5*X1*PECM)**2-PM1**2))
- PA2=SQRT(MAX(1E-10,(0.5*(2.-X1-X3)*PECM)**2-PM2**2))
- PA3=SQRT(MAX(1E-10,(0.5*X3*PECM)**2-PM3**2))
- CTHE2=(PA3**2-PA1**2-PA2**2)/(2.*PA1*PA2)
- CTHE3=(PA2**2-PA1**2-PA3**2)/(2.*PA1*PA3)
- IF(ABS(CTHE2).GE.1.001.OR.ABS(CTHE3).GE.1.001) MKERR=1
- CTHE3=MAX(-1.,MIN(1.,CTHE3))
- IF(MKERR.NE.0) CALL LUERRM(13,
- &'(LU3ENT:) unphysical kinematical variable setup')
-
-C...Store partons/particles in P vectors.
- P(IPA,3)=PA1
- P(IPA,4)=SQRT(PA1**2+PM1**2)
- P(IPA,5)=PM1
- P(IPA+2,1)=PA3*SQRT(1.-CTHE3**2)
- P(IPA+2,3)=PA3*CTHE3
- P(IPA+2,4)=SQRT(PA3**2+PM3**2)
- P(IPA+2,5)=PM3
- P(IPA+1,1)=-P(IPA+2,1)
- P(IPA+1,3)=-P(IPA,3)-P(IPA+2,3)
- P(IPA+1,4)=SQRT(P(IPA+1,1)**2+P(IPA+1,3)**2+PM2**2)
- P(IPA+1,5)=PM2
-
-C...Set N. Optionally fragment/decay.
- N=IPA+2
- IF(IP.EQ.0) CALL LUEXEC
-
- RETURN
- END