1 *CMZ : 17/07/98 15.44.34 by Federico Carminati
3 C*********************************************************************
5 SUBROUTINE LUJMAS(PMH,PML)
7 C...Purpose: to determine, approximately, the two jet masses that
8 C...minimize the sum m_H^2 + m_L^2, a la Clavelli and Wyler.
10 COMMON /LUJETS/ N,K(200000,5),P(200000,5),V(200000,5)
13 COMMON /LUDAT1/ MSTU(200),PARU(200),MSTJ(200),PARJ(200)
16 COMMON /LUDAT2/ KCHG(500,3),PMAS(500,4),PARF(2000),VCKM(4,4)
19 DIMENSION SM(3,3),SAX(3),PS(3,5)
30 C...Take copy of particles that are to be considered in mass analysis.
32 IF(K(I,1).LE.0.OR.K(I,1).GT.10) GOTO 150
33 IF(MSTU(41).GE.2) THEN
35 IF(KC.EQ.0.OR.KC.EQ.12.OR.KC.EQ.14.OR.KC.EQ.16.OR.
37 IF(MSTU(41).GE.3.AND.KCHG(KC,2).EQ.0.AND.LUCHGE(K(I,2)).EQ.0)
40 IF(N+NP+1.GE.MSTU(4)-MSTU(32)-5) THEN
41 CALL LUERRM(11,'(LUJMAS:) no more memory left in LUJETS')
49 IF(MSTU(42).EQ.0) P(N+NP,5)=0.
50 IF(MSTU(42).EQ.1.AND.K(I,2).NE.22) P(N+NP,5)=PMAS(101,1)
51 P(N+NP,4)=SQRT(P(N+NP,5)**2+P(I,1)**2+P(I,2)**2+P(I,3)**2)
53 C...Fill information in sphericity tensor and total momentum vector.
56 130 SM(J1,J2)=SM(J1,J2)+P(I,J1)*P(I,J2)
57 PSS=PSS+(P(I,1)**2+P(I,2)**2+P(I,3)**2)
59 140 PS(3,J)=PS(3,J)+P(N+NP,J)
62 C...Very low multiplicities (0 or 1) not considered.
64 CALL LUERRM(8,'(LUJMAS:) too few particles for analysis')
69 PARU(61)=SQRT(MAX(0.,PS(3,4)**2-PS(3,1)**2-PS(3,2)**2-PS(3,3)**2))
71 C...Find largest eigenvalue to matrix (third degree equation).
74 160 SM(J1,J2)=SM(J1,J2)/PSS
75 SQ=(SM(1,1)*SM(2,2)+SM(1,1)*SM(3,3)+SM(2,2)*SM(3,3)-SM(1,2)**2-
76 &SM(1,3)**2-SM(2,3)**2)/3.-1./9.
77 SR=-0.5*(SQ+1./9.+SM(1,1)*SM(2,3)**2+SM(2,2)*SM(1,3)**2+SM(3,3)*
78 &SM(1,2)**2-SM(1,1)*SM(2,2)*SM(3,3))+SM(1,2)*SM(1,3)*SM(2,3)+1./27.
79 SP=COS(ACOS(MAX(MIN(SR/SQRT(-SQ**3),1.),-1.))/3.)
80 SMA=1./3.+SQRT(-SQ)*MAX(2.*SP,SQRT(3.*(1.-SP**2))-SP)
82 C...Find largest eigenvector by solving equation system.
84 SM(J1,J1)=SM(J1,J1)-SMA
86 170 SM(J2,J1)=SM(J1,J2)
90 IF(ABS(SM(J1,J2)).LE.SMAX) GOTO 180
98 RL=SM(J1,JB)/SM(JA,JB)
100 SM(J1,J2)=SM(J1,J2)-RL*SM(JA,J2)
101 IF(ABS(SM(J1,J2)).LE.SMAX) GOTO 190
106 JB2=JB+2-3*((JB+1)/3)
109 SAX(JB)=-(SM(JA,JB1)*SAX(JB1)+SM(JA,JB2)*SAX(JB2))/SM(JA,JB)
111 C...Divide particles into two initial clusters by hemisphere.
113 PSAX=P(I,1)*SAX(1)+P(I,2)*SAX(2)+P(I,3)*SAX(3)
118 200 PS(IS,J)=PS(IS,J)+P(I,J)
119 PMS=MAX(1E-10,PS(1,4)**2-PS(1,1)**2-PS(1,2)**2-PS(1,3)**2)+
120 &MAX(1E-10,PS(2,4)**2-PS(2,1)**2-PS(2,2)**2-PS(2,3)**2)
122 C...Reassign one particle at a time; find maximum decrease of m^2 sum.
126 220 PS(3,J)=PS(1,J)-PS(2,J)
128 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)
129 IF(K(I,3).EQ.1) PMDI=2.*(P(I,5)**2-PPS)
130 IF(K(I,3).EQ.2) PMDI=2.*(P(I,5)**2+PPS)
137 C...Loop back if significant reduction in sum of m^2.
138 IF(PMD.LT.-PARU(48)*PMS) THEN
142 PS(IS,J)=PS(IS,J)-P(IM,J)
143 240 PS(3-IS,J)=PS(3-IS,J)+P(IM,J)
148 C...Final masses and output.
151 PS(1,5)=SQRT(MAX(0.,PS(1,4)**2-PS(1,1)**2-PS(1,2)**2-PS(1,3)**2))
152 PS(2,5)=SQRT(MAX(0.,PS(2,4)**2-PS(2,1)**2-PS(2,2)**2-PS(2,3)**2))
153 PMH=MAX(PS(1,5),PS(2,5))
154 PML=MIN(PS(1,5),PS(2,5))