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Commit | Line | Data |
---|---|---|
fe4da5cc | 1 | |
2 | C********************************************************************* | |
3 | ||
4 | SUBROUTINE PYSTGA(X,Q2,XPGA) | |
5 | ||
6 | C...Gives photon structure function. | |
7 | COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200) | |
8 | COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200) | |
9 | COMMON/PYINT1/MINT(400),VINT(400) | |
10 | SAVE /LUDAT1/ | |
11 | SAVE /PYPARS/,/PYINT1/ | |
12 | DIMENSION XPGA(-6:6),DGAG(4,3),DGBG(4,3),DGCG(4,3),DGAN(4,3), | |
13 | &DGBN(4,3),DGCN(4,3),DGDN(4,3),DGEN(4,3),DGAS(4,3),DGBS(4,3), | |
14 | &DGCS(4,3),DGDS(4,3),DGES(4,3) | |
15 | ||
16 | C...The following data lines are coefficients needed in the | |
17 | C...Drees and Grassie photon structure function parametrization. | |
18 | DATA DGAG/-.207E0,.6158E0,1.074E0,0.E0,.8926E-2,.6594E0, | |
19 | &.4766E0,.1975E-1,.03197E0,1.018E0,.2461E0,.2707E-1/ | |
20 | DATA DGBG/-.1987E0,.6257E0,8.352E0,5.024E0,.5085E-1,.2774E0, | |
21 | &-.3906E0,-.3212E0,-.618E-2,.9476E0,-.6094E0,-.1067E-1/ | |
22 | DATA DGCG/5.119E0,-.2752E0,-6.993E0,2.298E0,-.2313E0,.1382E0, | |
23 | &6.542E0,.5162E0,-.1216E0,.9047E0,2.653E0,.2003E-2/ | |
24 | DATA DGAN/2.285E0,-.1526E-1,1330.E0,4.219E0,-.3711E0,1.061E0, | |
25 | &4.758E0,-.1503E-1,15.8E0,-.9464E0,-.5E0,-.2118E0/ | |
26 | DATA DGBN/6.073E0,-.8132E0,-41.31E0,3.165E0,-.1717E0,.7815E0, | |
27 | &1.535E0,.7067E-2,2.742E0,-.7332E0,.7148E0,3.287E0/ | |
28 | DATA DGCN/-.4202E0,.1778E-1,.9216E0,.18E0,.8766E-1,.2197E-1, | |
29 | &.1096E0,.204E0,.2917E-1,.4657E-1,.1785E0,.4811E-1/ | |
30 | DATA DGDN/-.8083E-1,.6346E0,1.208E0,.203E0,-.8915E0,.2857E0, | |
31 | &2.973E0,.1185E0,-.342E-1,.7196E0,.7338E0,.8139E-1/ | |
32 | DATA DGEN/.5526E-1,1.136E0,.9512E0,.1163E-1,-.1816E0,.5866E0, | |
33 | &2.421E0,.4059E0,-.2302E-1,.9229E0,.5873E0,-.79E-4/ | |
34 | DATA DGAS/16.69E0,-.7916E0,1099.E0,4.428E0,-.1207E0,1.071E0, | |
35 | &1.977E0,-.8625E-2,6.734E0,-1.008E0,-.8594E-1,.7625E-1/ | |
36 | DATA DGBS/.176E0,.4794E-1,1.047E0,.25E-1,25.E0,-1.648E0, | |
37 | &-.1563E-1,6.438E0,59.88E0,-2.983E0,4.48E0,.9686E0/ | |
38 | DATA DGCS/-.208E-1,.3386E-2,4.853E0,.8404E0,-.123E-1,1.162E0, | |
39 | &.4824E0,-.11E-1,-.3226E-2,.8432E0,.3616E0,.1383E-2/ | |
40 | DATA DGDS/-.1685E-1,1.353E0,1.426E0,1.239E0,-.9194E-1,.7912E0, | |
41 | &.6397E0,2.327E0,-.3321E-1,.9475E0,-.3198E0,.2132E-1/ | |
42 | DATA DGES/-.1986E0,1.1E0,1.136E0,-.2779E0,.2015E-1,.9869E0, | |
43 | &-.7036E-1,.1694E-1,.1059E0,.6954E0,-.6663E0,.3683E0/ | |
44 | ||
45 | C...Photon structure function from Drees and Grassie. | |
46 | C...Allowed variable range: 1 GeV^2 < Q^2 < 10000 GeV^2. | |
47 | DO 100 KFL=-6,6 | |
48 | XPGA(KFL)=0. | |
49 | 100 CONTINUE | |
50 | VINT(231)=1. | |
51 | IF(MSTP(57).LE.0) THEN | |
52 | T=LOG(1./0.16) | |
53 | ELSE | |
54 | T=LOG(MIN(1E4,MAX(1.,Q2))/0.16) | |
55 | ENDIF | |
56 | X1=1.-X | |
57 | NF=3 | |
58 | IF(Q2.GT.25.) NF=4 | |
59 | IF(Q2.GT.300.) NF=5 | |
60 | NFE=NF-2 | |
61 | AEM=PARU(101) | |
62 | ||
63 | C...Evaluate gluon content. | |
64 | DGA=DGAG(1,NFE)*T**DGAG(2,NFE)+DGAG(3,NFE)*T**(-DGAG(4,NFE)) | |
65 | DGB=DGBG(1,NFE)*T**DGBG(2,NFE)+DGBG(3,NFE)*T**(-DGBG(4,NFE)) | |
66 | DGC=DGCG(1,NFE)*T**DGCG(2,NFE)+DGCG(3,NFE)*T**(-DGCG(4,NFE)) | |
67 | XPGL=DGA*X**DGB*X1**DGC | |
68 | ||
69 | C...Evaluate up- and down-type quark content. | |
70 | DGA=DGAN(1,NFE)*T**DGAN(2,NFE)+DGAN(3,NFE)*T**(-DGAN(4,NFE)) | |
71 | DGB=DGBN(1,NFE)*T**DGBN(2,NFE)+DGBN(3,NFE)*T**(-DGBN(4,NFE)) | |
72 | DGC=DGCN(1,NFE)*T**DGCN(2,NFE)+DGCN(3,NFE)*T**(-DGCN(4,NFE)) | |
73 | DGD=DGDN(1,NFE)*T**DGDN(2,NFE)+DGDN(3,NFE)*T**(-DGDN(4,NFE)) | |
74 | DGE=DGEN(1,NFE)*T**DGEN(2,NFE)+DGEN(3,NFE)*T**(-DGEN(4,NFE)) | |
75 | XPQN=X*(X**2+X1**2)/(DGA-DGB*LOG(X1))+DGC*X**DGD*X1**DGE | |
76 | DGA=DGAS(1,NFE)*T**DGAS(2,NFE)+DGAS(3,NFE)*T**(-DGAS(4,NFE)) | |
77 | DGB=DGBS(1,NFE)*T**DGBS(2,NFE)+DGBS(3,NFE)*T**(-DGBS(4,NFE)) | |
78 | DGC=DGCS(1,NFE)*T**DGCS(2,NFE)+DGCS(3,NFE)*T**(-DGCS(4,NFE)) | |
79 | DGD=DGDS(1,NFE)*T**DGDS(2,NFE)+DGDS(3,NFE)*T**(-DGDS(4,NFE)) | |
80 | DGE=DGES(1,NFE)*T**DGES(2,NFE)+DGES(3,NFE)*T**(-DGES(4,NFE)) | |
81 | DGF=9. | |
82 | IF(NF.EQ.4) DGF=10. | |
83 | IF(NF.EQ.5) DGF=55./6. | |
84 | XPQS=DGF*X*(X**2+X1**2)/(DGA-DGB*LOG(X1))+DGC*X**DGD*X1**DGE | |
85 | IF(NF.LE.3) THEN | |
86 | XPQU=(XPQS+9.*XPQN)/6. | |
87 | XPQD=(XPQS-4.5*XPQN)/6. | |
88 | ELSEIF(NF.EQ.4) THEN | |
89 | XPQU=(XPQS+6.*XPQN)/8. | |
90 | XPQD=(XPQS-6.*XPQN)/8. | |
91 | ELSE | |
92 | XPQU=(XPQS+7.5*XPQN)/10. | |
93 | XPQD=(XPQS-5.*XPQN)/10. | |
94 | ENDIF | |
95 | ||
96 | C...Put into output arrays. | |
97 | XPGA(0)=AEM*XPGL | |
98 | XPGA(1)=AEM*XPQD | |
99 | XPGA(2)=AEM*XPQU | |
100 | XPGA(3)=AEM*XPQD | |
101 | IF(NF.GE.4) XPGA(4)=AEM*XPQU | |
102 | IF(NF.GE.5) XPGA(5)=AEM*XPQD | |
103 | DO 110 KFL=1,6 | |
104 | XPGA(-KFL)=XPGA(KFL) | |
105 | 110 CONTINUE | |
106 | ||
107 | RETURN | |
108 | END |