| 3820ca8e |
1 | |
| 2 | CDECK ID>, HWBSPN. |
| 3 | |
| 4 | *CMZ :- -26/04/91 11.11.54 by Bryan Webber |
| 5 | |
| 6 | *-- Author : Ian Knowles |
| 7 | |
| 8 | C----------------------------------------------------------------------- |
| 9 | |
| 10 | SUBROUTINE HWBSPN |
| 11 | |
| 12 | C----------------------------------------------------------------------- |
| 13 | |
| 14 | C Constructs appropriate spin density/decay matrix for parton |
| 15 | |
| 16 | C in hard subprocess, othwise zero. Assignments based upon |
| 17 | |
| 18 | C Comp. Phys. Comm. 58 (1990) 271. |
| 19 | |
| 20 | C----------------------------------------------------------------------- |
| 21 | |
| 22 | INCLUDE 'HERWIG61.INC' |
| 23 | |
| 24 | DOUBLE PRECISION C,V12,V23,V13,TR,C1,C2,C3,R1(2),R2(2) |
| 25 | |
| 26 | INTEGER IST |
| 27 | |
| 28 | SAVE R1,R2,V12 |
| 29 | |
| 30 | IF (IERROR.NE.0) RETURN |
| 31 | |
| 32 | IST=MOD(ISTHEP(NEVPAR),10) |
| 33 | |
| 34 | C Assumed partons processed in the order IST=1,2,3,4 |
| 35 | |
| 36 | IF (IPROC.GE.100.AND.IPROC.LE.116) THEN |
| 37 | |
| 38 | C An e+e- ---> qqbar g event |
| 39 | |
| 40 | IF (IDPAR(2).EQ.13) THEN |
| 41 | |
| 42 | RHOPAR(1,2)=GPOLN |
| 43 | |
| 44 | RHOPAR(2,2)=0. |
| 45 | |
| 46 | RETURN |
| 47 | |
| 48 | ENDIF |
| 49 | |
| 50 | ELSEIF (IPRO.EQ.15.OR.IPRO.EQ.17) THEN |
| 51 | |
| 52 | IF (IHPRO.EQ. 7.OR.IHPRO.EQ. 8.OR. |
| 53 | |
| 54 | & IHPRO.EQ.10.OR.IHPRO.EQ.11.OR. |
| 55 | |
| 56 | & IHPRO.EQ.15.OR.IHPRO.EQ.16.OR. |
| 57 | |
| 58 | & (IHPRO.GE.21.AND.IHPRO.LE.31)) THEN |
| 59 | |
| 60 | C A hard 2 --- > 2 QCD subprocess involving gluons |
| 61 | |
| 62 | IF (IST.EQ.2) THEN |
| 63 | |
| 64 | CALL HWVEQU(2,RHOPAR(1,2),R1(1)) |
| 65 | |
| 66 | C=GCOEF(2)/GCOEF(1) |
| 67 | |
| 68 | DECPAR(1,2)=C*R1(1) |
| 69 | |
| 70 | DECPAR(2,2)=C*R1(2) |
| 71 | |
| 72 | RETURN |
| 73 | |
| 74 | ELSEIF (IST.EQ.3) THEN |
| 75 | |
| 76 | CALL HWVEQU(2,RHOPAR(1,2),R2(1)) |
| 77 | |
| 78 | V12=R1(1)*R2(1)+R1(2)*R2(2) |
| 79 | |
| 80 | TR=1./(GCOEF(1)+GCOEF(2)*V12) |
| 81 | |
| 82 | RHOPAR(1,2)= (GCOEF(3)*R1(1)+GCOEF(4)*R2(1))*TR |
| 83 | |
| 84 | RHOPAR(2,2)=-(GCOEF(3)*R1(2)+GCOEF(4)*R2(2))*TR |
| 85 | |
| 86 | RETURN |
| 87 | |
| 88 | ELSEIF (IST.EQ.4) THEN |
| 89 | |
| 90 | V13=R1(1)*DECPAR(1,2)+R1(2)*DECPAR(2,2) |
| 91 | |
| 92 | V23=R2(1)*DECPAR(1,2)+R2(2)*DECPAR(2,2) |
| 93 | |
| 94 | TR=1./(GCOEF(1)+GCOEF(2)*V12+GCOEF(3)*V13+GCOEF(4)*V23) |
| 95 | |
| 96 | C1=(GCOEF(2)+GCOEF(5))*TR |
| 97 | |
| 98 | C2=(GCOEF(3)+GCOEF(6))*TR |
| 99 | |
| 100 | C3=(GCOEF(4)+GCOEF(6))*TR |
| 101 | |
| 102 | RHOPAR(1,2)=C1*DECPAR(1,2)+C2*R2(1)+C3*R1(1) |
| 103 | |
| 104 | RHOPAR(2,2)=C1*DECPAR(2,2)-C2*R1(2)-C3*R2(2) |
| 105 | |
| 106 | RETURN |
| 107 | |
| 108 | ENDIF |
| 109 | |
| 110 | ENDIF |
| 111 | |
| 112 | ELSEIF (IPRO.EQ.16) THEN |
| 113 | |
| 114 | C A gluon fusion ---> Higgs event |
| 115 | |
| 116 | IF (IST.EQ.2) THEN |
| 117 | |
| 118 | DECPAR(1,2)=RHOPAR(1,2) |
| 119 | |
| 120 | DECPAR(2,2)=-RHOPAR(2,2) |
| 121 | |
| 122 | RETURN |
| 123 | |
| 124 | ENDIF |
| 125 | |
| 126 | ENDIF |
| 127 | |
| 128 | CALL HWVZRO(2,RHOPAR(1,2)) |
| 129 | |
| 130 | CALL HWVZRO(2,DECPAR(1,2)) |
| 131 | |
| 132 | END |
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