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Commit | Line | Data |
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3820ca8e | 1 | |
2 | CDECK ID>, HWUAER. | |
3 | ||
4 | *CMZ :- -23/08/94 13.22.29 by Mike Seymour | |
5 | ||
6 | *-- Author : Ian Knowles | |
7 | ||
8 | C----------------------------------------------------------------------- | |
9 | ||
10 | FUNCTION HWUAER(R) | |
11 | ||
12 | C----------------------------------------------------------------------- | |
13 | ||
14 | C Real part of photon self-energy: Pi_{gg}(R=M^2/Q^2) | |
15 | ||
16 | C----------------------------------------------------------------------- | |
17 | ||
18 | DOUBLE PRECISION HWUAER,R,ZERO,ONE,TWO,FOUR,FVTHR,THIRD,RMAX,BETA | |
19 | ||
20 | PARAMETER (ZERO=0.D0, ONE=1.D0, TWO=2.D0, FOUR=4.D0, | |
21 | ||
22 | & FVTHR=1.666666666666667D0, THIRD=.3333333333333333D0) | |
23 | ||
24 | PARAMETER (RMAX=1.D6) | |
25 | ||
26 | IF (ABS(R).LT.1.D-3) THEN | |
27 | ||
28 | C Use assymptotic formula | |
29 | ||
30 | HWUAER=-FVTHR-LOG(ABS(R)) | |
31 | ||
32 | ELSEIF (ABS(R).GT.RMAX) THEN | |
33 | ||
34 | HWUAER=ZERO | |
35 | ||
36 | ELSEIF (FOUR*R.GT.ONE) THEN | |
37 | ||
38 | BETA=SQRT(FOUR*R-ONE) | |
39 | ||
40 | HWUAER=THIRD | |
41 | ||
42 | & -(ONE+TWO*R)*(TWO-BETA*ACOS(ONE-ONE/(TWO*R))) | |
43 | ||
44 | ELSE | |
45 | ||
46 | BETA=SQRT(ONE-FOUR*R) | |
47 | ||
48 | HWUAER=THIRD | |
49 | ||
50 | & -(ONE+TWO*R)*(TWO+BETA*LOG(ABS((BETA-ONE)/(BETA+ONE)))) | |
51 | ||
52 | ENDIF | |
53 | ||
54 | RETURN | |
55 | ||
56 | END |