+++ /dev/null
-
-C*********************************************************************
-
- SUBROUTINE LUXDIF(NC,NJET,KFL,ECM,CHI,THE,PHI)
-
-C...Purpose: to give the angular orientation of events.
- 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...Charge. Factors depending on polarization for QED case.
- QF=KCHG(KFL,1)/3.
- POLL=1.-PARJ(131)*PARJ(132)
- POLD=PARJ(132)-PARJ(131)
- IF(MSTJ(102).LE.1.OR.MSTJ(109).EQ.1) THEN
- HF1=POLL
- HF2=0.
- HF3=PARJ(133)**2
- HF4=0.
-
-C...Factors depending on flavour, energy and polarization for QFD case.
- ELSE
- SFF=1./(16.*PARU(102)*(1.-PARU(102)))
- SFW=ECM**4/((ECM**2-PARJ(123)**2)**2+(PARJ(123)*PARJ(124))**2)
- SFI=SFW*(1.-(PARJ(123)/ECM)**2)
- AE=-1.
- VE=4.*PARU(102)-1.
- AF=SIGN(1.,QF)
- VF=AF-4.*QF*PARU(102)
- HF1=QF**2*POLL-2.*QF*VF*SFI*SFF*(VE*POLL-AE*POLD)+
- & (VF**2+AF**2)*SFW*SFF**2*((VE**2+AE**2)*POLL-2.*VE*AE*POLD)
- HF2=-2.*QF*AF*SFI*SFF*(AE*POLL-VE*POLD)+2.*VF*AF*SFW*SFF**2*
- & (2.*VE*AE*POLL-(VE**2+AE**2)*POLD)
- HF3=PARJ(133)**2*(QF**2-2.*QF*VF*SFI*SFF*VE+(VF**2+AF**2)*
- & SFW*SFF**2*(VE**2-AE**2))
- HF4=-PARJ(133)**2*2.*QF*VF*SFW*(PARJ(123)*PARJ(124)/ECM**2)*
- & SFF*AE
- ENDIF
-
-C...Mass factor. Differential cross-sections for two-jet events.
- SQ2=SQRT(2.)
- QME=0.
- IF(MSTJ(103).GE.4.AND.IABS(MSTJ(101)).LE.1.AND.MSTJ(102).LE.1.AND.
- &MSTJ(109).NE.1) QME=(2.*ULMASS(KFL)/ECM)**2
- IF(NJET.EQ.2) THEN
- SIGU=4.*SQRT(1.-QME)
- SIGL=2.*QME*SQRT(1.-QME)
- SIGT=0.
- SIGI=0.
- SIGA=0.
- SIGP=4.
-
-C...Kinematical variables. Reduce four-jet event to three-jet one.
- ELSE
- IF(NJET.EQ.3) THEN
- X1=2.*P(NC+1,4)/ECM
- X2=2.*P(NC+3,4)/ECM
- ELSE
- ECMR=P(NC+1,4)+P(NC+4,4)+SQRT((P(NC+2,1)+P(NC+3,1))**2+
- & (P(NC+2,2)+P(NC+3,2))**2+(P(NC+2,3)+P(NC+3,3))**2)
- X1=2.*P(NC+1,4)/ECMR
- X2=2.*P(NC+4,4)/ECMR
- ENDIF
-
-C...Differential cross-sections for three-jet (or reduced four-jet).
- XQ=(1.-X1)/(1.-X2)
- CT12=(X1*X2-2.*X1-2.*X2+2.+QME)/SQRT((X1**2-QME)*(X2**2-QME))
- ST12=SQRT(1.-CT12**2)
- IF(MSTJ(109).NE.1) THEN
- SIGU=2.*X1**2+X2**2*(1.+CT12**2)-QME*(3.+CT12**2-X1-X2)-
- & QME*X1/XQ+0.5*QME*((X2**2-QME)*ST12**2-2.*X2)*XQ
- SIGL=(X2*ST12)**2-QME*(3.-CT12**2-2.5*(X1+X2)+X1*X2+QME)+
- & 0.5*QME*(X1**2-X1-QME)/XQ+0.5*QME*((X2**2-QME)*CT12**2-X2)*XQ
- SIGT=0.5*(X2**2-QME-0.5*QME*(X2**2-QME)/XQ)*ST12**2
- SIGI=((1.-0.5*QME*XQ)*(X2**2-QME)*ST12*CT12+QME*(1.-X1-X2+
- & 0.5*X1*X2+0.5*QME)*ST12/CT12)/SQ2
- SIGA=X2**2*ST12/SQ2
- SIGP=2.*(X1**2-X2**2*CT12)
-
-C...Differential cross-sect for scalar gluons (no mass effects).
- ELSE
- X3=2.-X1-X2
- XT=X2*ST12
- CT13=SQRT(MAX(0.,1.-(XT/X3)**2))
- SIGU=(1.-PARJ(171))*(X3**2-0.5*XT**2)+
- & PARJ(171)*(X3**2-0.5*XT**2-4.*(1.-X1)*(1.-X2)**2/X1)
- SIGL=(1.-PARJ(171))*0.5*XT**2+
- & PARJ(171)*0.5*(1.-X1)**2*XT**2
- SIGT=(1.-PARJ(171))*0.25*XT**2+
- & PARJ(171)*0.25*XT**2*(1.-2.*X1)
- SIGI=-(0.5/SQ2)*((1.-PARJ(171))*XT*X3*CT13+
- & PARJ(171)*XT*((1.-2.*X1)*X3*CT13-X1*(X1-X2)))
- SIGA=(0.25/SQ2)*XT*(2.*(1.-X1)-X1*X3)
- SIGP=X3**2-2.*(1.-X1)*(1.-X2)/X1
- ENDIF
- ENDIF
-
-C...Upper bounds for differential cross-section.
- HF1A=ABS(HF1)
- HF2A=ABS(HF2)
- HF3A=ABS(HF3)
- HF4A=ABS(HF4)
- SIGMAX=(2.*HF1A+HF3A+HF4A)*ABS(SIGU)+2.*(HF1A+HF3A+HF4A)*
- &ABS(SIGL)+2.*(HF1A+2.*HF3A+2.*HF4A)*ABS(SIGT)+2.*SQ2*
- &(HF1A+2.*HF3A+2.*HF4A)*ABS(SIGI)+4.*SQ2*HF2A*ABS(SIGA)+
- &2.*HF2A*ABS(SIGP)
-
-C...Generate angular orientation according to differential cross-sect.
- 100 CHI=PARU(2)*RLU(0)
- CTHE=2.*RLU(0)-1.
- PHI=PARU(2)*RLU(0)
- CCHI=COS(CHI)
- SCHI=SIN(CHI)
- C2CHI=COS(2.*CHI)
- S2CHI=SIN(2.*CHI)
- THE=ACOS(CTHE)
- STHE=SIN(THE)
- C2PHI=COS(2.*(PHI-PARJ(134)))
- S2PHI=SIN(2.*(PHI-PARJ(134)))
- SIG=((1.+CTHE**2)*HF1+STHE**2*(C2PHI*HF3-S2PHI*HF4))*SIGU+
- &2.*(STHE**2*HF1-STHE**2*(C2PHI*HF3-S2PHI*HF4))*SIGL+
- &2.*(STHE**2*C2CHI*HF1+((1.+CTHE**2)*C2CHI*C2PHI-2.*CTHE*S2CHI*
- &S2PHI)*HF3-((1.+CTHE**2)*C2CHI*S2PHI+2.*CTHE*S2CHI*C2PHI)*HF4)*
- &SIGT-2.*SQ2*(2.*STHE*CTHE*CCHI*HF1-2.*STHE*(CTHE*CCHI*C2PHI-
- &SCHI*S2PHI)*HF3+2.*STHE*(CTHE*CCHI*S2PHI+SCHI*C2PHI)*HF4)*SIGI+
- &4.*SQ2*STHE*CCHI*HF2*SIGA+2.*CTHE*HF2*SIGP
- IF(SIG.LT.SIGMAX*RLU(0)) GOTO 100
-
- RETURN
- END