* $Id$ C********************************************************************* SUBROUTINE LUX3JT_HIJING(NJET,CUT,KFL,ECM,X1,X2) C...Purpose: to select the kinematical variables of three-jet events. #include "ludat1_hijing.inc" DIMENSION ZHUP(5,12) C...Coefficients of Zhu second order parametrization. DATA ((ZHUP(IC1,IC2),IC2=1,12),IC1=1,5)/ & 18.29, 89.56, 4.541, -52.09, -109.8, 24.90, & 11.63, 3.683, 17.50, 0.002440, -1.362, -0.3537, & 11.42, 6.299, -22.55, -8.915, 59.25, -5.855, & -32.85, -1.054, -16.90, 0.006489, -0.8156, 0.01095, & 7.847, -3.964, -35.83, 1.178, 29.39, 0.2806, & 47.82, -12.36, -56.72, 0.04054, -0.4365, 0.6062, & 5.441, -56.89, -50.27, 15.13, 114.3, -18.19, & 97.05, -1.890, -139.9, 0.08153, -0.4984, 0.9439, & -17.65, 51.44, -58.32, 70.95, -255.7, -78.99, & 476.9, 29.65, -239.3, 0.4745, -1.174, 6.081/ C...Dilogarithm of x for x<0.5 (x>0.5 obtained by analytic trick). DILOG(X)=X+X**2/4.+X**3/9.+X**4/16.+X**5/25.+X**6/36.+X**7/49. C...Event type. Mass effect factors and other common constants. MSTJ(120)=2 MSTJ(121)=0 PMQ=ULMASS_HIJING(KFL) QME=(2.*PMQ/ECM)**2 IF(MSTJ(109).NE.1) THEN CUTL=LOG(CUT) CUTD=LOG(1./CUT-2.) IF(MSTJ(109).EQ.0) THEN CF=4./3. CN=3. TR=2. WTMX=MIN(20.,37.-6.*CUTD) IF(MSTJ(110).EQ.2) WTMX=2.*(7.5+80.*CUT) ELSE CF=1. CN=0. TR=12. WTMX=0. ENDIF C...Alpha_strong and effects of optimized Q^2 scale. Maximum weight. ALS2PI=PARU(118)/PARU(2) WTOPT=0. IF(MSTJ(111).EQ.1) WTOPT=(33.-2.*MSTU(112))/6.*LOG(PARJ(169))* & ALS2PI WTMAX=MAX(0.,1.+WTOPT+ALS2PI*WTMX) C...Choose three-jet events in allowed region. 100 NJET=3 110 Y13L=CUTL+CUTD*RLU_HIJING(0) Y23L=CUTL+CUTD*RLU_HIJING(0) Y13=EXP(Y13L) Y23=EXP(Y23L) Y12=1.-Y13-Y23 IF(Y12.LE.CUT) GOTO 110 IF(Y13**2+Y23**2+2.*Y12.LE.2.*RLU_HIJING(0)) GOTO 110 C...Second order corrections. IF(MSTJ(101).EQ.2.AND.MSTJ(110).LE.1) THEN Y12L=LOG(Y12) Y13M=LOG(1.-Y13) Y23M=LOG(1.-Y23) Y12M=LOG(1.-Y12) IF(Y13.LE.0.5) Y13I=DILOG(Y13) IF(Y13.GE.0.5) Y13I=1.644934-Y13L*Y13M-DILOG(1.-Y13) IF(Y23.LE.0.5) Y23I=DILOG(Y23) IF(Y23.GE.0.5) Y23I=1.644934-Y23L*Y23M-DILOG(1.-Y23) IF(Y12.LE.0.5) Y12I=DILOG(Y12) IF(Y12.GE.0.5) Y12I=1.644934-Y12L*Y12M-DILOG(1.-Y12) WT1=(Y13**2+Y23**2+2.*Y12)/(Y13*Y23) WT2=CF*(-2.*(CUTL-Y12L)**2-3.*CUTL-1.+3.289868+ & 2.*(2.*CUTL-Y12L)*CUT/Y12)+ & CN*((CUTL-Y12L)**2-(CUTL-Y13L)**2-(CUTL-Y23L)**2-11.*CUTL/6.+ & 67./18.+1.644934-(2.*CUTL-Y12L)*CUT/Y12+(2.*CUTL-Y13L)* & CUT/Y13+(2.*CUTL-Y23L)*CUT/Y23)+ & TR*(2.*CUTL/3.-10./9.)+ & CF*(Y12/(Y12+Y13)+Y12/(Y12+Y23)+(Y12+Y23)/Y13+(Y12+Y13)/Y23+ & Y13L*(4.*Y12**2+2.*Y12*Y13+4.*Y12*Y23+Y13*Y23)/(Y12+Y23)**2+ & Y23L*(4.*Y12**2+2.*Y12*Y23+4.*Y12*Y13+Y13*Y23)/(Y12+Y13)**2)/ & WT1+ & CN*(Y13L*Y13/(Y12+Y23)+Y23L*Y23/(Y12+Y13))/WT1+ & (CN-2.*CF)*((Y12**2+(Y12+Y13)**2)*(Y12L*Y23L-Y12L*Y12M-Y23L* & Y23M+1.644934-Y12I-Y23I)/(Y13*Y23)+(Y12**2+(Y12+Y23)**2)* & (Y12L*Y13L-Y12L*Y12M-Y13L*Y13M+1.644934-Y12I-Y13I)/ & (Y13*Y23)+(Y13**2+Y23**2)/(Y13*Y23*(Y13+Y23))- & 2.*Y12L*Y12**2/(Y13+Y23)**2-4.*Y12L*Y12/(Y13+Y23))/WT1- & CN*(Y13L*Y23L-Y13L*Y13M-Y23L*Y23M+1.644934-Y13I-Y23I) IF(1.+WTOPT+ALS2PI*WT2.LE.0.) MSTJ(121)=1 IF(1.+WTOPT+ALS2PI*WT2.LE.WTMAX*RLU_HIJING(0)) GOTO 110 PARJ(156)=(WTOPT+ALS2PI*WT2)/(1.+WTOPT+ALS2PI*WT2) ELSEIF(MSTJ(101).EQ.2.AND.MSTJ(110).EQ.2) THEN C...Second order corrections; Zhu parametrization of ERT. ZX=(Y23-Y13)**2 ZY=1.-Y12 IZA=0 DO 120 IY=1,5 120 IF(ABS(CUT-0.01*IY).LT.0.0001) IZA=IY IF(IZA.NE.0) THEN IZ=IZA WT2=ZHUP(IZ,1)+ZHUP(IZ,2)*ZX+ZHUP(IZ,3)*ZX**2+(ZHUP(IZ,4)+ & ZHUP(IZ,5)*ZX)*ZY+(ZHUP(IZ,6)+ZHUP(IZ,7)*ZX)*ZY**2+ & (ZHUP(IZ,8)+ZHUP(IZ,9)*ZX)*ZY**3+ZHUP(IZ,10)/(ZX-ZY**2)+ & ZHUP(IZ,11)/(1.-ZY)+ZHUP(IZ,12)/ZY ELSE IZ=100.*CUT WTL=ZHUP(IZ,1)+ZHUP(IZ,2)*ZX+ZHUP(IZ,3)*ZX**2+(ZHUP(IZ,4)+ & ZHUP(IZ,5)*ZX)*ZY+(ZHUP(IZ,6)+ZHUP(IZ,7)*ZX)*ZY**2+ & (ZHUP(IZ,8)+ZHUP(IZ,9)*ZX)*ZY**3+ZHUP(IZ,10)/(ZX-ZY**2)+ & ZHUP(IZ,11)/(1.-ZY)+ZHUP(IZ,12)/ZY IZ=IZ+1 WTU=ZHUP(IZ,1)+ZHUP(IZ,2)*ZX+ZHUP(IZ,3)*ZX**2+(ZHUP(IZ,4)+ & ZHUP(IZ,5)*ZX)*ZY+(ZHUP(IZ,6)+ZHUP(IZ,7)*ZX)*ZY**2+ & (ZHUP(IZ,8)+ZHUP(IZ,9)*ZX)*ZY**3+ZHUP(IZ,10)/(ZX-ZY**2)+ & ZHUP(IZ,11)/(1.-ZY)+ZHUP(IZ,12)/ZY WT2=WTL+(WTU-WTL)*(100.*CUT+1.-IZ) ENDIF IF(1.+WTOPT+2.*ALS2PI*WT2.LE.0.) MSTJ(121)=1 IF(1.+WTOPT+2.*ALS2PI*WT2.LE.WTMAX*RLU_HIJING(0)) GOTO 110 PARJ(156)=(WTOPT+2.*ALS2PI*WT2)/(1.+WTOPT+2.*ALS2PI*WT2) ENDIF C...Impose mass cuts (gives two jets). For fixed jet number new try. X1=1.-Y23 X2=1.-Y13 X3=1.-Y12 IF(4.*Y23*Y13*Y12/X3**2.LE.QME) NJET=2 IF(MOD(MSTJ(103),4).GE.2.AND.IABS(MSTJ(101)).LE.1.AND.QME*X3+ & 0.5*QME**2+(0.5*QME+0.25*QME**2)*((1.-X2)/(1.-X1)+ & (1.-X1)/(1.-X2)).GT.(X1**2+X2**2)*RLU_HIJING(0)) NJET=2 IF(MSTJ(101).EQ.-1.AND.NJET.EQ.2) GOTO 100 C...Scalar gluon model (first order only, no mass effects). ELSE 130 NJET=3 140 Y12=SQRT(4.*CUT**2+RLU_HIJING(0)*((1.-CUT)**2-4.*CUT**2)) IF(LOG((Y12-CUT)/CUT).LE.RLU_HIJING(0)*LOG((1.-2.*CUT)/CUT)) $ GOTO 140 YD=SIGN(2.*CUT*((Y12-CUT)/CUT)**RLU_HIJING(0)-Y12,RLU_HIJING(0) $ -0.5) X1=1.-0.5*(Y12+YD) X2=1.-0.5*(Y12-YD) IF(4.*(1.-X1)*(1.-X2)*Y12/(1.-Y12)**2.LE.QME) NJET=2 IF(MSTJ(101).EQ.-1.AND.NJET.EQ.2) GOTO 130 ENDIF RETURN END