[u/mrichter/AliRoot.git] / HERWIG / src / hwbazf.f


CDECK  ID>, HWBAZF.

*CMZ :-        -26/04/91  11.11.54  by  Bryan Webber

*-- Author :    Ian Knowles

C-----------------------------------------------------------------------

      SUBROUTINE HWBAZF(IPAR,JPAR,VEC1,VEC2,VEC3,VEC)

C-----------------------------------------------------------------------

C     Azimuthal correlation functions for Collins' algorithm,

C     see I.G.Knowles, Comp. Phys. Comm. 58 (90) 271 for notation.

C-----------------------------------------------------------------------

      INCLUDE 'HERWIG61.INC'

      DOUBLE PRECISION Z1,Z2,DOT12,DOT23,DOT31,TR,FN(7),VEC1(2),VEC2(2),

     & VEC3(2),VEC(2)

      INTEGER IPAR,JPAR

      LOGICAL GLUI,GLUJ

      IF (.NOT.AZSPIN) RETURN

      Z1=PPAR(4,JPAR)/PPAR(4,IPAR)

      Z2=1.-Z1

      GLUI=IDPAR(IPAR).EQ.13

      GLUJ=IDPAR(JPAR).EQ.13

      IF (GLUI) THEN

         IF (GLUJ) THEN

C           Branching: g--->gg

            FN(2)=Z2/Z1

            FN(3)=1./FN(2)

            FN(4)=Z1*Z2

            FN(1)=FN(2)+FN(3)+FN(4)

            FN(5)=FN(2)+2.*Z1

            FN(6)=FN(3)+2.*Z2

            FN(7)=FN(4)-2.

         ELSE

C           Branching: g--->qqbar

            FN(1)=(Z1*Z1+Z2*Z2)/2.

            FN(2)=0.

            FN(3)=0.

            FN(4)=-Z1*Z2

            FN(5)=-(2.*Z1-1.)/2.

            FN(6)=-FN(5)

            FN(7)=FN(1)

         ENDIF

      ELSE

         IF (GLUJ) THEN

C           Branching: q--->gq

            FN(1)=(1.+Z2*Z2)/(2.*Z1)

            FN(2)=Z2/Z1

            FN(3)=0.

            FN(4)=0.

            FN(5)=FN(1)

            FN(6)=(1.+Z2)/2.

            FN(7)=-FN(6)

         ELSE

C           Branching: q--->qg

            FN(1)=(1.+Z1*Z1)/(2.*Z2)

            FN(2)=0.

            FN(3)=Z1/Z2

            FN(4)=0.

            FN(5)=(1.+Z1)/2.

            FN(6)=FN(1)

            FN(7)=-FN(5)

         ENDIF

      ENDIF

      DOT12=VEC1(1)*VEC2(1)+VEC1(2)*VEC2(2)

      DOT23=VEC2(1)*VEC3(1)+VEC2(2)*VEC3(2)

      DOT31=VEC3(1)*VEC1(1)+VEC3(2)*VEC1(2)

      TR=1./(FN(1)+FN(2)*DOT23+FN(3)*DOT31+FN(4)*DOT12)

      VEC(1)=((FN(2)+FN(5)*DOT23)*VEC1(1)

     &       +(FN(3)+FN(6)*DOT31)*VEC2(1)

     &       +(FN(4)+FN(7)*DOT12)*VEC3(1))*TR

      VEC(2)=((FN(2)+FN(5)*DOT23)*VEC1(2)

     &       +(FN(3)+FN(6)*DOT31)*VEC2(2)

     &       +(FN(4)+FN(7)*DOT12)*VEC3(2))*TR

      END
Commit	Line	Data
3820ca8e	1
	2	CDECK ID>, HWBAZF.
	3
	4	*CMZ :- -26/04/91 11.11.54 by Bryan Webber
	5
	6	*-- Author : Ian Knowles
	7
	8	C-----------------------------------------------------------------------
	9
	10	SUBROUTINE HWBAZF(IPAR,JPAR,VEC1,VEC2,VEC3,VEC)
	11
	12	C-----------------------------------------------------------------------
	13
	14	C Azimuthal correlation functions for Collins' algorithm,
	15
	16	C see I.G.Knowles, Comp. Phys. Comm. 58 (90) 271 for notation.
	17
	18	C-----------------------------------------------------------------------
	19
	20	INCLUDE 'HERWIG61.INC'
	21
	22	DOUBLE PRECISION Z1,Z2,DOT12,DOT23,DOT31,TR,FN(7),VEC1(2),VEC2(2),
	23
	24	& VEC3(2),VEC(2)
	25
	26	INTEGER IPAR,JPAR
	27
	28	LOGICAL GLUI,GLUJ
	29
	30	IF (.NOT.AZSPIN) RETURN
	31
	32	Z1=PPAR(4,JPAR)/PPAR(4,IPAR)
	33
	34	Z2=1.-Z1
	35
	36	GLUI=IDPAR(IPAR).EQ.13
	37
	38	GLUJ=IDPAR(JPAR).EQ.13
	39
	40	IF (GLUI) THEN
	41
	42	IF (GLUJ) THEN
	43
	44	C Branching: g--->gg
	45
	46	FN(2)=Z2/Z1
	47
	48	FN(3)=1./FN(2)
	49
	50	FN(4)=Z1*Z2
	51
	52	FN(1)=FN(2)+FN(3)+FN(4)
	53
	54	FN(5)=FN(2)+2.*Z1
	55
	56	FN(6)=FN(3)+2.*Z2
	57
	58	FN(7)=FN(4)-2.
	59
	60	ELSE
	61
	62	C Branching: g--->qqbar
	63
	64	FN(1)=(Z1Z1+Z2Z2)/2.
65
66	FN(2)=0.
67
68	FN(3)=0.
69
70	FN(4)=-Z1*Z2
71
72	FN(5)=-(2.*Z1-1.)/2.
73
74	FN(6)=-FN(5)
75
76	FN(7)=FN(1)
77
78	ENDIF
79
80	ELSE
81
82	IF (GLUJ) THEN
83
84	C Branching: q--->gq
85
86	FN(1)=(1.+Z2Z2)/(2.Z1)
87
88	FN(2)=Z2/Z1
89
90	FN(3)=0.
91
92	FN(4)=0.
93
94	FN(5)=FN(1)
95
96	FN(6)=(1.+Z2)/2.
97
98	FN(7)=-FN(6)
99
100	ELSE
101
102	C Branching: q--->qg
103
104	FN(1)=(1.+Z1Z1)/(2.Z2)
105
106	FN(2)=0.
107
108	FN(3)=Z1/Z2
109
110	FN(4)=0.
111
112	FN(5)=(1.+Z1)/2.
113
114	FN(6)=FN(1)
115
116	FN(7)=-FN(5)
117
118	ENDIF
119
120	ENDIF
121
122	DOT12=VEC1(1)VEC2(1)+VEC1(2)VEC2(2)
123
124	DOT23=VEC2(1)VEC3(1)+VEC2(2)VEC3(2)
125
126	DOT31=VEC3(1)VEC1(1)+VEC3(2)VEC1(2)
127
128	TR=1./(FN(1)+FN(2)DOT23+FN(3)DOT31+FN(4)*DOT12)
129
130	VEC(1)=((FN(2)+FN(5)DOT23)VEC1(1)
131
132	& +(FN(3)+FN(6)DOT31)VEC2(1)
133
134	& +(FN(4)+FN(7)DOT12)VEC3(1))*TR
135
136	VEC(2)=((FN(2)+FN(5)DOT23)VEC1(2)
137
138	& +(FN(3)+FN(6)DOT31)VEC2(2)
139
140	& +(FN(4)+FN(7)DOT12)VEC3(2))*TR
141
142	END