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Commit | Line | Data |
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fe4da5cc | 1 | *CMZ : 17/07/98 15.44.35 by Federico Carminati |
2 | *-- Author : | |
3 | C********************************************************************* | |
4 | ||
5 | SUBROUTINE LURADK(ECM,MK,PAK,THEK,PHIK,ALPK) | |
6 | ||
7 | C...Purpose: to generate initial state photon radiation. | |
8 | *KEEP,LUDAT1. | |
9 | COMMON /LUDAT1/ MSTU(200),PARU(200),MSTJ(200),PARJ(200) | |
10 | SAVE /LUDAT1/ | |
11 | *KEND. | |
12 | ||
13 | C...Function: cumulative hard photon spectrum in QFD case. | |
14 | FXK(XX)=2.*LOG(XX)+PARJ(161)*LOG(1.-XX)+PARJ(162)*XX+ | |
15 | &PARJ(163)*LOG((XX-SZM)**2+SZW**2)+PARJ(164)*ATAN((XX-SZM)/SZW) | |
16 | ||
17 | C...Determine whether radiative photon or not. | |
18 | MK=0 | |
19 | PAK=0. | |
20 | IF(PARJ(160).LT.RLU(0)) RETURN | |
21 | MK=1 | |
22 | ||
23 | C...Photon energy range. Find photon momentum in QED case. | |
24 | XKL=PARJ(135) | |
25 | XKU=MIN(PARJ(136),1.-(2.*PARJ(127)/ECM)**2) | |
26 | IF(MSTJ(102).LE.1) THEN | |
27 | 100 XK=1./(1.+(1./XKL-1.)*((1./XKU-1.)/(1./XKL-1.))**RLU(0)) | |
28 | IF(1.+(1.-XK)**2.LT.2.*RLU(0)) GOTO 100 | |
29 | ||
30 | C...Ditto in QFD case, by numerical inversion of integrated spectrum. | |
31 | ELSE | |
32 | SZM=1.-(PARJ(123)/ECM)**2 | |
33 | SZW=PARJ(123)*PARJ(124)/ECM**2 | |
34 | FXKL=FXK(XKL) | |
35 | FXKU=FXK(XKU) | |
36 | FXKD=1E-4*(FXKU-FXKL) | |
37 | FXKR=FXKL+RLU(0)*(FXKU-FXKL) | |
38 | NXK=0 | |
39 | 110 NXK=NXK+1 | |
40 | XK=0.5*(XKL+XKU) | |
41 | FXKV=FXK(XK) | |
42 | IF(FXKV.GT.FXKR) THEN | |
43 | XKU=XK | |
44 | FXKU=FXKV | |
45 | ELSE | |
46 | XKL=XK | |
47 | FXKL=FXKV | |
48 | ENDIF | |
49 | IF(NXK.LT.15.AND.FXKU-FXKL.GT.FXKD) GOTO 110 | |
50 | XK=XKL+(XKU-XKL)*(FXKR-FXKL)/(FXKU-FXKL) | |
51 | ENDIF | |
52 | PAK=0.5*ECM*XK | |
53 | ||
54 | C...Photon polar and azimuthal angle. | |
55 | PME=2.*(ULMASS(11)/ECM)**2 | |
56 | 120 CTHM=PME*(2./PME)**RLU(0) | |
57 | IF(1.-(XK**2*CTHM*(1.-0.5*CTHM)+2.*(1.-XK)*PME/MAX(PME, | |
58 | &CTHM*(1.-0.5*CTHM)))/(1.+(1.-XK)**2).LT.RLU(0)) GOTO 120 | |
59 | CTHE=1.-CTHM | |
60 | IF(RLU(0).GT.0.5) CTHE=-CTHE | |
61 | STHE=SQRT(MAX(0.,(CTHM-PME)*(2.-CTHM))) | |
62 | THEK=ULANGL(CTHE,STHE) | |
63 | PHIK=PARU(2)*RLU(0) | |
64 | ||
65 | C...Rotation angle for hadronic system. | |
66 | SGN=1. | |
67 | IF(0.5*(2.-XK*(1.-CTHE))**2/((2.-XK)**2+(XK*CTHE)**2).GT. | |
68 | &RLU(0)) SGN=-1. | |
69 | ALPK=ASIN(SGN*STHE*(XK-SGN*(2.*SQRT(1.-XK)-2.+XK)*CTHE)/ | |
70 | &(2.-XK*(1.-SGN*CTHE))) | |
71 | ||
72 | RETURN | |
73 | END |