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Commit | Line | Data |
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fe4da5cc | 1 | |
2 | C********************************************************************* | |
3 | ||
4 | FUNCTION ULALPS(Q2) | |
5 | ||
6 | C...Purpose: to give the value of alpha_strong. | |
7 | COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200) | |
8 | COMMON/LUDAT2/KCHG(500,3),PMAS(500,4),PARF(2000),VCKM(4,4) | |
9 | SAVE /LUDAT1/,/LUDAT2/ | |
10 | ||
11 | C...Constant alpha_strong trivial. | |
12 | IF(MSTU(111).LE.0) THEN | |
13 | ULALPS=PARU(111) | |
14 | MSTU(118)=MSTU(112) | |
15 | PARU(117)=0. | |
16 | PARU(118)=PARU(111) | |
17 | RETURN | |
18 | ENDIF | |
19 | ||
20 | C...Find effective Q2, number of flavours and Lambda. | |
21 | Q2EFF=Q2 | |
22 | IF(MSTU(115).GE.2) Q2EFF=MAX(Q2,PARU(114)) | |
23 | NF=MSTU(112) | |
24 | ALAM2=PARU(112)**2 | |
25 | 100 IF(NF.GT.MAX(2,MSTU(113))) THEN | |
26 | Q2THR=PARU(113)*PMAS(NF,1)**2 | |
27 | IF(Q2EFF.LT.Q2THR) THEN | |
28 | NF=NF-1 | |
29 | ALAM2=ALAM2*(Q2THR/ALAM2)**(2./(33.-2.*NF)) | |
30 | GOTO 100 | |
31 | ENDIF | |
32 | ENDIF | |
33 | 110 IF(NF.LT.MIN(8,MSTU(114))) THEN | |
34 | Q2THR=PARU(113)*PMAS(NF+1,1)**2 | |
35 | IF(Q2EFF.GT.Q2THR) THEN | |
36 | NF=NF+1 | |
37 | ALAM2=ALAM2*(ALAM2/Q2THR)**(2./(33.-2.*NF)) | |
38 | GOTO 110 | |
39 | ENDIF | |
40 | ENDIF | |
41 | IF(MSTU(115).EQ.1) Q2EFF=Q2EFF+ALAM2 | |
42 | PARU(117)=SQRT(ALAM2) | |
43 | ||
44 | C...Evaluate first or second order alpha_strong. | |
45 | B0=(33.-2.*NF)/6. | |
46 | ALGQ=LOG(MAX(1.0001,Q2EFF/ALAM2)) | |
47 | IF(MSTU(111).EQ.1) THEN | |
48 | ULALPS=MIN(PARU(115),PARU(2)/(B0*ALGQ)) | |
49 | ELSE | |
50 | B1=(153.-19.*NF)/6. | |
51 | ULALPS=MIN(PARU(115),PARU(2)/(B0*ALGQ)*(1.-B1*LOG(ALGQ)/ | |
52 | & (B0**2*ALGQ))) | |
53 | ENDIF | |
54 | MSTU(118)=NF | |
55 | PARU(118)=ULALPS | |
56 | ||
57 | RETURN | |
58 | END |