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Commit | Line | Data |
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3820ca8e | 1 | |
2 | CDECK ID>, HWUALF. | |
3 | ||
4 | *CMZ :- -15/07/92 14.08.45 by Mike Seymour | |
5 | ||
6 | *-- Author : Bryan Webber | |
7 | ||
8 | C----------------------------------------------------------------------- | |
9 | ||
10 | FUNCTION HWUALF(IOPT,SCALE) | |
11 | ||
12 | C----------------------------------------------------------------------- | |
13 | ||
14 | C STRONG COUPLING CONSTANT | |
15 | ||
16 | C IOPT.EQ.0 INITIALIZES | |
17 | ||
18 | C .EQ.1 TWO-LOOP, FLAVOUR THRESHOLDS | |
19 | ||
20 | C .EQ.2 RATIO OF ABOVE TO ONE-LOOP | |
21 | ||
22 | C WITH 5-FLAVOUR BETA, LAMBDA=QCDL3 | |
23 | ||
24 | C .EQ.3 ONE-LOOP WITH 5-FLAVOUR BETA, LAMBDA=QCDL3 | |
25 | ||
26 | C----------------------------------------------------------------------- | |
27 | ||
28 | INCLUDE 'HERWIG61.INC' | |
29 | ||
30 | DOUBLE PRECISION HWUALF,SCALE,KAFAC,B3,B4,B5,B6,C3,C4,C5,C6,C35, | |
31 | ||
32 | & C45,C65,D35,RHO,RAT,RLF,DRH,EPS | |
33 | ||
34 | INTEGER IOPT,ITN | |
35 | ||
36 | SAVE B3,B4,B5,B6,C3,C4,C5,C6,C35,C45,C65,D35 | |
37 | ||
38 | DATA EPS/1.D-6/ | |
39 | ||
40 | IF (IOPT.EQ.0) THEN | |
41 | ||
42 | C---INITIALIZE CONSTANTS | |
43 | ||
44 | CAFAC=FLOAT(NCOLO) | |
45 | ||
46 | CFFAC=FLOAT(NCOLO**2-1)/(2.*CAFAC) | |
47 | ||
48 | B3=((11.*CAFAC)- 6.)/(12.*PIFAC) | |
49 | ||
50 | B4=((11.*CAFAC)- 8.)/(12.*PIFAC) | |
51 | ||
52 | B5=((11.*CAFAC)-10.)/(12.*PIFAC) | |
53 | ||
54 | B6=((11.*CAFAC)-12.)/(12.*PIFAC) | |
55 | ||
56 | BETAF=6.*PIFAC*B5 | |
57 | ||
58 | C3=((17.*CAFAC**2)-(5.*CAFAC+3.*CFFAC)*3.)/(24.*PIFAC**2)/B3**2 | |
59 | ||
60 | C4=((17.*CAFAC**2)-(5.*CAFAC+3.*CFFAC)*4.)/(24.*PIFAC**2)/B4**2 | |
61 | ||
62 | C5=((17.*CAFAC**2)-(5.*CAFAC+3.*CFFAC)*5.)/(24.*PIFAC**2)/B5**2 | |
63 | ||
64 | C6=((17.*CAFAC**2)-(5.*CAFAC+3.*CFFAC)*6.)/(24.*PIFAC**2)/B6**2 | |
65 | ||
66 | KAFAC=CAFAC*(67./18.-PIFAC**2/6.)-25./9. | |
67 | ||
68 | C---QCDLAM IS 5-FLAVOUR LAMBDA-MS-BAR AT LARGE X OR Z | |
69 | ||
70 | C---QCDL5 IS 5-FLAVOUR LAMBDA-MC | |
71 | ||
72 | QCDL5=QCDLAM*EXP(KAFAC/(4.*PIFAC*B5))/SQRT(2.D0) | |
73 | ||
74 | C---COMPUTE THRESHOLD MATCHING | |
75 | ||
76 | RHO=2.*LOG(RMASS(6)/QCDL5) | |
77 | ||
78 | RAT=LOG(RHO)/RHO | |
79 | ||
80 | C65=(B5/(1.-C5*RAT)-B6/(1.-C6*RAT))*RHO | |
81 | ||
82 | RHO=2.*LOG(RMASS(5)/QCDL5) | |
83 | ||
84 | RAT=LOG(RHO)/RHO | |
85 | ||
86 | C45=(B5/(1.-C5*RAT)-B4/(1.-C4*RAT))*RHO | |
87 | ||
88 | RHO=2.*LOG(RMASS(4)/QCDL5) | |
89 | ||
90 | RAT=LOG(RHO)/RHO | |
91 | ||
92 | C35=(B4/(1.-C4*RAT)-B3/(1.-C3*RAT))*RHO+C45 | |
93 | ||
94 | C---FIND QCDL3 | |
95 | ||
96 | D35=-1./(B3*C35) | |
97 | ||
98 | DO 10 ITN=1,100 | |
99 | ||
100 | RAT=LOG(D35)/D35 | |
101 | ||
102 | RLF=B3*D35/(1.-C3*RAT) | |
103 | ||
104 | DRH=B3*(RLF+C35)*D35**2/((1.-2.*C3*RAT+C3/D35)*RLF**2) | |
105 | ||
106 | D35=D35-DRH | |
107 | ||
108 | IF (ABS(DRH).LT.EPS*D35) GOTO 20 | |
109 | ||
110 | 10 CONTINUE | |
111 | ||
112 | 20 QCDL3=QCDL5*EXP(0.5*D35) | |
113 | ||
114 | ENDIF | |
115 | ||
116 | IF (SCALE.LE.QCDL5) CALL HWWARN('HWUALF',51,*999) | |
117 | ||
118 | RHO=2.*LOG(SCALE/QCDL5) | |
119 | ||
120 | IF (IOPT.EQ.3) THEN | |
121 | ||
122 | IF (RHO.LE.D35) CALL HWWARN('HWUALF',52,*999) | |
123 | ||
124 | HWUALF=1./(B5*(RHO-D35)) | |
125 | ||
126 | RETURN | |
127 | ||
128 | ENDIF | |
129 | ||
130 | RAT=LOG(RHO)/RHO | |
131 | ||
132 | IF (SCALE.GT.RMASS(6)) THEN | |
133 | ||
134 | RLF=B6*RHO/(1.-C6*RAT)+C65 | |
135 | ||
136 | ELSEIF (SCALE.GT.RMASS(5)) THEN | |
137 | ||
138 | RLF=B5*RHO/(1.-C5*RAT) | |
139 | ||
140 | ELSEIF (SCALE.GT.RMASS(4)) THEN | |
141 | ||
142 | RLF=B4*RHO/(1.-C4*RAT)+C45 | |
143 | ||
144 | ELSE | |
145 | ||
146 | RLF=B3*RHO/(1.-C3*RAT)+C35 | |
147 | ||
148 | ENDIF | |
149 | ||
150 | IF (RLF.LE.ZERO) CALL HWWARN('HWUALF',53,*999) | |
151 | ||
152 | IF (IOPT.EQ.1) THEN | |
153 | ||
154 | HWUALF=1./RLF | |
155 | ||
156 | ELSE | |
157 | ||
158 | HWUALF=B5*(RHO-D35)/RLF | |
159 | ||
160 | IF (HWUALF.GT.ONE) CALL HWWARN('HWUALF',54,*999) | |
161 | ||
162 | ENDIF | |
163 | ||
164 | RETURN | |
165 | ||
166 | 999 HWUALF=ZERO | |
167 | ||
168 | END |