C********************************************************************* SUBROUTINE LUONIA(KFL,ECM) C...Purpose: to generate Upsilon and toponium decays into three C...gluons or two gluons and a photon. 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...Printout. Check input parameters. IF(MSTU(12).GE.1) CALL LULIST(0) IF(KFL.LT.0.OR.KFL.GT.8) THEN CALL LUERRM(16,'(LUONIA:) called with unknown flavour code') IF(MSTU(21).GE.1) RETURN ENDIF IF(ECM.LT.PARJ(127)+2.02*PARF(101)) THEN CALL LUERRM(16,'(LUONIA:) called with too small CM energy') IF(MSTU(21).GE.1) RETURN ENDIF C...Initial e+e- and onium state (optional). NC=0 IF(MSTJ(115).GE.2) THEN NC=NC+2 CALL LU1ENT(NC-1,11,0.5*ECM,0.,0.) K(NC-1,1)=21 CALL LU1ENT(NC,-11,0.5*ECM,PARU(1),0.) K(NC,1)=21 ENDIF KFLC=IABS(KFL) IF(MSTJ(115).GE.3.AND.KFLC.GE.5) THEN NC=NC+1 KF=110*KFLC+3 MSTU10=MSTU(10) MSTU(10)=1 P(NC,5)=ECM CALL LU1ENT(NC,KF,ECM,0.,0.) K(NC,1)=21 K(NC,3)=1 MSTU(10)=MSTU10 ENDIF C...Choose x1 and x2 according to matrix element. NTRY=0 100 X1=RLU(0) X2=RLU(0) X3=2.-X1-X2 IF(X3.GE.1..OR.((1.-X1)/(X2*X3))**2+((1.-X2)/(X1*X3))**2+ &((1.-X3)/(X1*X2))**2.LE.2.*RLU(0)) GOTO 100 NTRY=NTRY+1 NJET=3 IF(MSTJ(101).LE.4) CALL LU3ENT(NC+1,21,21,21,ECM,X1,X3) IF(MSTJ(101).GE.5) CALL LU3ENT(-(NC+1),21,21,21,ECM,X1,X3) C...Photon-gluon-gluon events. Small system modifications. Jet origin. MSTU(111)=MSTJ(108) IF(MSTJ(108).EQ.2.AND.(MSTJ(101).EQ.0.OR.MSTJ(101).EQ.1)) &MSTU(111)=1 PARU(112)=PARJ(121) IF(MSTU(111).EQ.2) PARU(112)=PARJ(122) QF=0. IF(KFLC.NE.0) QF=KCHG(KFLC,1)/3. RGAM=7.2*QF**2*PARU(101)/ULALPS(ECM**2) MK=0 ECMC=ECM IF(RLU(0).GT.RGAM/(1.+RGAM)) THEN IF(1.-MAX(X1,X2,X3).LE.MAX((PARJ(126)/ECM)**2,PARJ(125))) & NJET=2 IF(NJET.EQ.2.AND.MSTJ(101).LE.4) CALL LU2ENT(NC+1,21,21,ECM) IF(NJET.EQ.2.AND.MSTJ(101).GE.5) CALL LU2ENT(-(NC+1),21,21,ECM) ELSE MK=1 ECMC=SQRT(1.-X1)*ECM IF(ECMC.LT.2.*PARJ(127)) GOTO 100 K(NC+1,1)=1 K(NC+1,2)=22 K(NC+1,4)=0 K(NC+1,5)=0 IF(MSTJ(101).GE.5) K(NC+2,4)=MSTU(5)*(NC+3) IF(MSTJ(101).GE.5) K(NC+2,5)=MSTU(5)*(NC+3) IF(MSTJ(101).GE.5) K(NC+3,4)=MSTU(5)*(NC+2) IF(MSTJ(101).GE.5) K(NC+3,5)=MSTU(5)*(NC+2) NJET=2 IF(ECMC.LT.4.*PARJ(127)) THEN MSTU10=MSTU(10) MSTU(10)=1 P(NC+2,5)=ECMC CALL LU1ENT(NC+2,83,0.5*(X2+X3)*ECM,PARU(1),0.) MSTU(10)=MSTU10 NJET=0 ENDIF ENDIF DO 110 IP=NC+1,N K(IP,3)=K(IP,3)+(MSTJ(115)/2)+(KFLC/5)*(MSTJ(115)/3)*(NC-1) 110 CONTINUE C...Differential cross-sections. Upper limit for cross-section. IF(MSTJ(106).EQ.1) THEN SQ2=SQRT(2.) HF1=1.-PARJ(131)*PARJ(132) HF3=PARJ(133)**2 CT13=(X1*X3-2.*X1-2.*X3+2.)/(X1*X3) ST13=SQRT(1.-CT13**2) SIGL=0.5*X3**2*((1.-X2)**2+(1.-X3)**2)*ST13**2 SIGU=(X1*(1.-X1))**2+(X2*(1.-X2))**2+(X3*(1.-X3))**2-SIGL SIGT=0.5*SIGL SIGI=(SIGL*CT13/ST13+0.5*X1*X3*(1.-X2)**2*ST13)/SQ2 SIGMAX=(2.*HF1+HF3)*ABS(SIGU)+2.*(HF1+HF3)*ABS(SIGL)+2.*(HF1+ & 2.*HF3)*ABS(SIGT)+2.*SQ2*(HF1+2.*HF3)*ABS(SIGI) C...Angular orientation of event. 120 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)*SIGU+2.*(STHE**2*HF1- & STHE**2*C2PHI*HF3)*SIGL+2.*(STHE**2*C2CHI*HF1+((1.+CTHE**2)* & C2CHI*C2PHI-2.*CTHE*S2CHI*S2PHI)*HF3)*SIGT-2.*SQ2*(2.*STHE*CTHE* & CCHI*HF1-2.*STHE*(CTHE*CCHI*C2PHI-SCHI*S2PHI)*HF3)*SIGI IF(SIG.LT.SIGMAX*RLU(0)) GOTO 120 CALL LUDBRB(NC+1,N,0.,CHI,0D0,0D0,0D0) CALL LUDBRB(NC+1,N,THE,PHI,0D0,0D0,0D0) ENDIF C...Generate parton shower. Rearrange along strings and check. IF(MSTJ(101).GE.5.AND.NJET.GE.2) THEN CALL LUSHOW(NC+MK+1,-NJET,ECMC) MSTJ14=MSTJ(14) IF(MSTJ(105).EQ.-1) MSTJ(14)=-1 IF(MSTJ(105).GE.0) MSTU(28)=0 CALL LUPREP(0) MSTJ(14)=MSTJ14 IF(MSTJ(105).GE.0.AND.MSTU(28).NE.0) GOTO 100 ENDIF C...Generate fragmentation. Information for LUTABU: IF(MSTJ(105).EQ.1) CALL LUEXEC MSTU(161)=110*KFLC+3 MSTU(162)=0 RETURN END