C********************************************************************* SUBROUTINE LUJMAS(PMH,PML) C...Purpose: to determine, approximately, the two jet masses that C...minimize the sum m_H^2 + m_L^2, a la Clavelli and Wyler. 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/ DIMENSION SM(3,3),SAX(3),PS(3,5) C...Reset. NP=0 DO 120 J1=1,3 DO 100 J2=J1,3 SM(J1,J2)=0. 100 CONTINUE DO 110 J2=1,4 PS(J1,J2)=0. 110 CONTINUE 120 CONTINUE PSS=0. C...Take copy of particles that are to be considered in mass analysis. DO 170 I=1,N IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 170 IF(MSTU(41).GE.2) THEN KC=LUCOMP(K(I,2)) IF(KC.EQ.0.OR.KC.EQ.12.OR.KC.EQ.14.OR.KC.EQ.16.OR. & KC.EQ.18) GOTO 170 IF(MSTU(41).GE.3.AND.KCHG(KC,2).EQ.0.AND.LUCHGE(K(I,2)).EQ.0) & GOTO 170 ENDIF IF(N+NP+1.GE.MSTU(4)-MSTU(32)-5) THEN CALL LUERRM(11,'(LUJMAS:) no more memory left in LUJETS') PMH=-2. PML=-2. RETURN ENDIF NP=NP+1 DO 130 J=1,5 P(N+NP,J)=P(I,J) 130 CONTINUE IF(MSTU(42).EQ.0) P(N+NP,5)=0. IF(MSTU(42).EQ.1.AND.K(I,2).NE.22) P(N+NP,5)=PMAS(101,1) P(N+NP,4)=SQRT(P(N+NP,5)**2+P(I,1)**2+P(I,2)**2+P(I,3)**2) C...Fill information in sphericity tensor and total momentum vector. DO 150 J1=1,3 DO 140 J2=J1,3 SM(J1,J2)=SM(J1,J2)+P(I,J1)*P(I,J2) 140 CONTINUE 150 CONTINUE PSS=PSS+(P(I,1)**2+P(I,2)**2+P(I,3)**2) DO 160 J=1,4 PS(3,J)=PS(3,J)+P(N+NP,J) 160 CONTINUE 170 CONTINUE C...Very low multiplicities (0 or 1) not considered. IF(NP.LE.1) THEN CALL LUERRM(8,'(LUJMAS:) too few particles for analysis') PMH=-1. PML=-1. RETURN ENDIF PARU(61)=SQRT(MAX(0.,PS(3,4)**2-PS(3,1)**2-PS(3,2)**2-PS(3,3)**2)) C...Find largest eigenvalue to matrix (third degree equation). DO 190 J1=1,3 DO 180 J2=J1,3 SM(J1,J2)=SM(J1,J2)/PSS 180 CONTINUE 190 CONTINUE SQ=(SM(1,1)*SM(2,2)+SM(1,1)*SM(3,3)+SM(2,2)*SM(3,3)-SM(1,2)**2- &SM(1,3)**2-SM(2,3)**2)/3.-1./9. SR=-0.5*(SQ+1./9.+SM(1,1)*SM(2,3)**2+SM(2,2)*SM(1,3)**2+SM(3,3)* &SM(1,2)**2-SM(1,1)*SM(2,2)*SM(3,3))+SM(1,2)*SM(1,3)*SM(2,3)+1./27. SP=COS(ACOS(MAX(MIN(SR/SQRT(-SQ**3),1.),-1.))/3.) SMA=1./3.+SQRT(-SQ)*MAX(2.*SP,SQRT(3.*(1.-SP**2))-SP) C...Find largest eigenvector by solving equation system. DO 210 J1=1,3 SM(J1,J1)=SM(J1,J1)-SMA DO 200 J2=J1+1,3 SM(J2,J1)=SM(J1,J2) 200 CONTINUE 210 CONTINUE SMAX=0. DO 230 J1=1,3 DO 220 J2=1,3 IF(ABS(SM(J1,J2)).LE.SMAX) GOTO 220 JA=J1 JB=J2 SMAX=ABS(SM(J1,J2)) 220 CONTINUE 230 CONTINUE SMAX=0. DO 250 J3=JA+1,JA+2 J1=J3-3*((J3-1)/3) RL=SM(J1,JB)/SM(JA,JB) DO 240 J2=1,3 SM(J1,J2)=SM(J1,J2)-RL*SM(JA,J2) IF(ABS(SM(J1,J2)).LE.SMAX) GOTO 240 JC=J1 SMAX=ABS(SM(J1,J2)) 240 CONTINUE 250 CONTINUE JB1=JB+1-3*(JB/3) JB2=JB+2-3*((JB+1)/3) SAX(JB1)=-SM(JC,JB2) SAX(JB2)=SM(JC,JB1) SAX(JB)=-(SM(JA,JB1)*SAX(JB1)+SM(JA,JB2)*SAX(JB2))/SM(JA,JB) C...Divide particles into two initial clusters by hemisphere. DO 270 I=N+1,N+NP PSAX=P(I,1)*SAX(1)+P(I,2)*SAX(2)+P(I,3)*SAX(3) IS=1 IF(PSAX.LT.0.) IS=2 K(I,3)=IS DO 260 J=1,4 PS(IS,J)=PS(IS,J)+P(I,J) 260 CONTINUE 270 CONTINUE PMS=MAX(1E-10,PS(1,4)**2-PS(1,1)**2-PS(1,2)**2-PS(1,3)**2)+ &MAX(1E-10,PS(2,4)**2-PS(2,1)**2-PS(2,2)**2-PS(2,3)**2) C...Reassign one particle at a time; find maximum decrease of m^2 sum. 280 PMD=0. IM=0 DO 290 J=1,4 PS(3,J)=PS(1,J)-PS(2,J) 290 CONTINUE DO 300 I=N+1,N+NP PPS=P(I,4)*PS(3,4)-P(I,1)*PS(3,1)-P(I,2)*PS(3,2)-P(I,3)*PS(3,3) IF(K(I,3).EQ.1) PMDI=2.*(P(I,5)**2-PPS) IF(K(I,3).EQ.2) PMDI=2.*(P(I,5)**2+PPS) IF(PMDI.LT.PMD) THEN PMD=PMDI IM=I ENDIF 300 CONTINUE C...Loop back if significant reduction in sum of m^2. IF(PMD.LT.-PARU(48)*PMS) THEN PMS=PMS+PMD IS=K(IM,3) DO 310 J=1,4 PS(IS,J)=PS(IS,J)-P(IM,J) PS(3-IS,J)=PS(3-IS,J)+P(IM,J) 310 CONTINUE K(IM,3)=3-IS GOTO 280 ENDIF C...Final masses and output. MSTU(61)=N+1 MSTU(62)=NP PS(1,5)=SQRT(MAX(0.,PS(1,4)**2-PS(1,1)**2-PS(1,2)**2-PS(1,3)**2)) PS(2,5)=SQRT(MAX(0.,PS(2,4)**2-PS(2,1)**2-PS(2,2)**2-PS(2,3)**2)) PMH=MAX(PS(1,5),PS(2,5)) PML=MIN(PS(1,5),PS(2,5)) RETURN END