Merging the VirtualMC branch to the main development branch (HEAD)
[u/mrichter/AliRoot.git] / HIJING / hipyset1_35 / ulalps_hijing.F
CommitLineData
e74335a4 1* $Id$
2
3C*********************************************************************
4
5 FUNCTION ULALPS_HIJING(Q2)
6
7C...Purpose: to give the value of alpha_strong.
8#include "ludat1_hijing.inc"
9#include "ludat2_hijing.inc"
10
11C...Constant alpha_strong trivial.
12 IF(MSTU(111).LE.0) THEN
13 ULALPS_HIJING=PARU(111)
14 MSTU(118)=MSTU(112)
15 PARU(117)=0.
16 PARU(118)=PARU(111)
17 RETURN
18 ENDIF
19
20C...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
44C...Evaluate first or second order alpha_strong.
45 B0=(33.-2.*NF)/6.
46 ALGQ=LOG(Q2EFF/ALAM2)
47 IF(MSTU(111).EQ.1) THEN
48 ULALPS_HIJING=PARU(2)/(B0*ALGQ)
49 ELSE
50 B1=(153.-19.*NF)/6.
51 ULALPS_HIJING=PARU(2)/(B0*ALGQ)*(1.-B1*LOG(ALGQ)/(B0**2*ALGQ))
52 ENDIF
53 MSTU(118)=NF
54 PARU(118)=ULALPS_HIJING
55
56 RETURN
57 END