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pystfu.F
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pystfu.F
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SUBROUTINE PYSTFU(KF,X,Q2,XPQ)
C...Gives electron, photon, pi+, neutron, proton and hyperon
C...structure functions according to a few different parametrizations.
C...Note that what is coded is x times the probability distribution,
C...i.e. xq(x,Q2) etc.
COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
COMMON/LUDAT2/KCHG(500,3),PMAS(500,4),PARF(2000),VCKM(4,4)
COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
COMMON/PYINT1/MINT(400),VINT(400)
COMMON/PYINT8/XPVMD(-6:6),XPANL(-6:6),XPANH(-6:6),XPBEH(-6:6),
&XPDIR(-6:6)
SAVE /LUDAT1/,/LUDAT2/
SAVE /PYPARS/,/PYINT1/,/PYINT8/
DIMENSION XPQ(-25:25),XPEL(-25:25),XPGA(-6:6),XPPI(-6:6),
&XPPR(-6:6)
C...Interface to PDFLIB.
COMMON/W50513/XMIN,XMAX,Q2MIN,Q2MAX
SAVE /W50513/
DOUBLE PRECISION XX,QQ,UPV,DNV,USEA,DSEA,STR,CHM,BOT,TOP,GLU,
&VALUE(20),XMIN,XMAX,Q2MIN,Q2MAX
CHARACTER*20 PARM(20)
DATA VALUE/20*0D0/,PARM/20*' '/
C...Data related to Schuler-Sjostrand photon distributions.
DATA ALAMGA/0.2/, PMCGA/1.3/, PMBGA/4.6/
C...Reset structure functions.
MINT(92)=0
DO 100 KFL=-25,25
XPQ(KFL)=0.
100 CONTINUE
C...Check x and particle species.
IF(X.LE.0..OR.X.GE.1.) THEN
WRITE(MSTU(11),5000) X
RETURN
ENDIF
KFA=IABS(KF)
IF(KFA.NE.11.AND.KFA.NE.22.AND.KFA.NE.211.AND.KFA.NE.2112.AND.
&KFA.NE.2212.AND.KFA.NE.3122.AND.KFA.NE.3112.AND.KFA.NE.3212
&.AND.KFA.NE.3222.AND.KFA.NE.3312.AND.KFA.NE.3322.AND.
&KFA.NE.3334.AND.KFA.NE.111) THEN
WRITE(MSTU(11),5100) KF
RETURN
ENDIF
C...Electron structure function call.
IF(KFA.EQ.11) THEN
CALL PYSTEL(X,Q2,XPEL)
DO 110 KFL=-25,25
XPQ(KFL)=XPEL(KFL)
110 CONTINUE
C...Photon structure function call (VDM+anomalous).
ELSEIF(KFA.EQ.22.AND.MINT(109).LE.1) THEN
IF(MSTP(56).EQ.1.AND.MSTP(55).EQ.1) THEN
CALL PYSTGA(X,Q2,XPGA)
DO 120 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
120 CONTINUE
ELSEIF(MSTP(56).EQ.1.AND.MSTP(55).GE.5.AND.MSTP(55).LE.8) THEN
Q2MX=Q2
P2MX=0.36
IF(MSTP(55).GE.7) P2MX=4.0
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGGAM(MSTP(55)-4,X,Q2MX,0.,F2GAM,XPGA)
DO 130 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
130 CONTINUE
VINT(231)=P2MX
ELSEIF(MSTP(56).EQ.1.AND.MSTP(55).GE.9.AND.MSTP(55).LE.12) THEN
Q2MX=Q2
P2MX=0.36
IF(MSTP(55).GE.11) P2MX=4.0
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGGAM(MSTP(55)-8,X,Q2MX,0.,F2GAM,XPGA)
DO 140 KFL=-6,6
XPQ(KFL)=XPVMD(KFL)+XPANL(KFL)+XPBEH(KFL)+XPDIR(KFL)
140 CONTINUE
VINT(231)=P2MX
ELSEIF(MSTP(56).EQ.2) THEN
C...Call PDFLIB structure functions.
PARM(1)='NPTYPE'
VALUE(1)=3
PARM(2)='NGROUP'
VALUE(2)=MSTP(55)/1000
PARM(3)='NSET'
VALUE(3)=MOD(MSTP(55),1000)
IF(MINT(93).NE.3000000+MSTP(55)) THEN
CALL PDFSET(PARM,VALUE)
MINT(93)=3000000+MSTP(55)
ENDIF
XX=X
QQ=SQRT(MAX(0.,SNGL(Q2MIN),Q2))
IF(MSTP(57).EQ.0) QQ=SQRT(Q2MIN)
CALL STRUCTM(XX,QQ,UPV,DNV,USEA,DSEA,STR,CHM,BOT,TOP,GLU)
VINT(231)=Q2MIN
XPQ(0)=GLU
XPQ(1)=DNV
XPQ(-1)=DNV
XPQ(2)=UPV
XPQ(-2)=UPV
XPQ(3)=STR
XPQ(-3)=STR
XPQ(4)=CHM
XPQ(-4)=CHM
XPQ(5)=BOT
XPQ(-5)=BOT
XPQ(6)=TOP
XPQ(-6)=TOP
ELSE
WRITE(MSTU(11),5200) KF,MSTP(56),MSTP(55)
ENDIF
C...Pion/gammaVDM structure function call.
ELSEIF(KFA.EQ.211.OR.KFA.EQ.111.OR.(KFA.EQ.22.AND.
&MINT(109).EQ.2)) THEN
IF(KFA.EQ.22.AND.MSTP(56).EQ.1.AND.MSTP(55).GE.5.AND.
& MSTP(55).LE.12) THEN
ISET=1+MOD(MSTP(55)-1,4)
Q2MX=Q2
P2MX=0.36
IF(ISET.GE.3) P2MX=4.0
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGVMD(ISET,2,X,Q2MX,P2MX,ALAMGA,XPGA)
DO 150 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
150 CONTINUE
VINT(231)=P2MX
ELSEIF(MSTP(54).EQ.1.AND.MSTP(53).GE.1.AND.MSTP(53).LE.3) THEN
CALL PYSTPI(X,Q2,XPPI)
DO 160 KFL=-6,6
XPQ(KFL)=XPPI(KFL)
160 CONTINUE
ELSEIF(MSTP(54).EQ.2) THEN
C...Call PDFLIB structure functions.
PARM(1)='NPTYPE'
VALUE(1)=2
PARM(2)='NGROUP'
VALUE(2)=MSTP(53)/1000
PARM(3)='NSET'
VALUE(3)=MOD(MSTP(53),1000)
IF(MINT(93).NE.2000000+MSTP(53)) THEN
CALL PDFSET(PARM,VALUE)
MINT(93)=2000000+MSTP(53)
ENDIF
XX=X
QQ=SQRT(MAX(0.,SNGL(Q2MIN),Q2))
IF(MSTP(57).EQ.0) QQ=SQRT(Q2MIN)
CALL STRUCTM(XX,QQ,UPV,DNV,USEA,DSEA,STR,CHM,BOT,TOP,GLU)
VINT(231)=Q2MIN
XPQ(0)=GLU
XPQ(1)=DSEA
XPQ(-1)=UPV+DSEA
XPQ(2)=UPV+USEA
XPQ(-2)=USEA
XPQ(3)=STR
XPQ(-3)=STR
XPQ(4)=CHM
XPQ(-4)=CHM
XPQ(5)=BOT
XPQ(-5)=BOT
XPQ(6)=TOP
XPQ(-6)=TOP
ELSE
WRITE(MSTU(11),5200) KF,MSTP(54),MSTP(53)
ENDIF
C...Anomalous photon structure function call.
ELSEIF(KFA.EQ.22.AND.MINT(109).EQ.3) THEN
Q2MX=Q2
P2MX=PARP(15)**2
IF(MSTP(56).EQ.1.AND.MSTP(55).LE.8) THEN
IF(MSTP(55).EQ.5.OR.MSTP(55).EQ.6) P2MX=0.36
IF(MSTP(55).EQ.7.OR.MSTP(55).EQ.8) P2MX=4.0
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGANO(0,X,Q2MX,P2MX,ALAMGA,XPGA)
DO 170 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
170 CONTINUE
VINT(231)=P2MX
ELSEIF(MSTP(56).EQ.1) THEN
IF(MSTP(55).EQ.9.OR.MSTP(55).EQ.10) P2MX=0.36
IF(MSTP(55).EQ.11.OR.MSTP(55).EQ.12) P2MX=4.0
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGGAM(MSTP(55)-8,X,Q2MX,0.,F2GM,XPGA)
DO 180 KFL=-6,6
XPQ(KFL)=MAX(0.,XPANL(KFL)+XPBEH(KFL)+XPDIR(KFL))
180 CONTINUE
VINT(231)=P2MX
ELSEIF(MSTP(56).EQ.2) THEN
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGANO(0,X,Q2MX,P2MX,ALAMGA,XPGA)
DO 185 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
185 CONTINUE
VINT(231)=P2MX
ELSEIF(MSTP(55).GE.1.AND.MSTP(55).LE.5) THEN
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGVMD(0,MSTP(55),X,Q2MX,P2MX,PARP(1),XPGA)
DO 190 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
190 CONTINUE
VINT(231)=P2MX
ELSE
200 RKF=11.*RLU(0)
KFR=1
IF(RKF.GT.1.) KFR=2
IF(RKF.GT.5.) KFR=3
IF(RKF.GT.6.) KFR=4
IF(RKF.GT.10.) KFR=5
IF(KFR.EQ.4.AND.Q2.LT.PMCGA**2) GOTO 200
IF(KFR.EQ.5.AND.Q2.LT.PMBGA**2) GOTO 200
IF(MSTP(57).EQ.0) Q2MX=P2MX
CALL PYGVMD(0,KFR,X,Q2MX,P2MX,PARP(1),XPGA)
DO 210 KFL=-6,6
XPQ(KFL)=XPGA(KFL)
210 CONTINUE
VINT(231)=P2MX
ENDIF
C...Proton structure function call.
ELSE
IF(MSTP(52).EQ.1.AND.MSTP(51).GE.1.AND.MSTP(51).LE.11) THEN
CALL PYSTPR(X,Q2,XPPR)
DO 220 KFL=-6,6
XPQ(KFL)=XPPR(KFL)
220 CONTINUE
ELSEIF(MSTP(52).EQ.2) THEN
C...Call PDFLIB structure functions.
PARM(1)='NPTYPE'
VALUE(1)=1
PARM(2)='NGROUP'
VALUE(2)=MSTP(51)/1000
PARM(3)='NSET'
VALUE(3)=MOD(MSTP(51),1000)
IF(MINT(93).NE.1000000+MSTP(51)) THEN
CALL PDFSET(PARM,VALUE)
MINT(93)=1000000+MSTP(51)
ENDIF
XX=X
QQ=SQRT(MAX(0.,SNGL(Q2MIN),Q2))
IF(MSTP(57).EQ.0) QQ=SQRT(Q2MIN)
CALL STRUCTM(XX,QQ,UPV,DNV,USEA,DSEA,STR,CHM,BOT,TOP,GLU)
VINT(231)=Q2MIN
XPQ(0)=GLU
XPQ(1)=DNV+DSEA
XPQ(-1)=DSEA
XPQ(2)=UPV+USEA
XPQ(-2)=USEA
XPQ(3)=STR
XPQ(-3)=STR
XPQ(4)=CHM
XPQ(-4)=CHM
XPQ(5)=BOT
XPQ(-5)=BOT
XPQ(6)=TOP
XPQ(-6)=TOP
ELSE
WRITE(MSTU(11),5200) KF,MSTP(52),MSTP(51)
ENDIF
ENDIF
C...Isospin average for pi0/gammaVDM.
IF(KFA.EQ.111.OR.(KFA.EQ.22.AND.MINT(109).EQ.2)) THEN
IF(KFA.EQ.22.AND.MSTP(55).GE.5.AND.MSTP(55).LE.12) THEN
XPV=XPQ(2)-XPQ(1)
XPQ(2)=XPQ(1)
XPQ(-2)=XPQ(-1)
ELSE
XPS=0.5*(XPQ(1)+XPQ(-2))
XPV=0.5*(XPQ(2)+XPQ(-1))-XPS
XPQ(2)=XPS
XPQ(-1)=XPS
ENDIF
IF(KFA.EQ.22.AND.MINT(105).LE.223) THEN
XPQ(1)=XPQ(1)+0.2*XPV
XPQ(-1)=XPQ(-1)+0.2*XPV
XPQ(2)=XPQ(2)+0.8*XPV
XPQ(-2)=XPQ(-2)+0.8*XPV
ELSEIF(KFA.EQ.22.AND.MINT(105).EQ.333) THEN
XPQ(3)=XPQ(3)+XPV
XPQ(-3)=XPQ(-3)+XPV
ELSEIF(KFA.EQ.22.AND.MINT(105).EQ.443) THEN
XPQ(4)=XPQ(4)+XPV
XPQ(-4)=XPQ(-4)+XPV
IF(MSTP(55).GE.9) THEN
DO 230 KFL=-6,6
XPQ(KFL)=0.
230 CONTINUE
ENDIF
ELSE
XPQ(1)=XPQ(1)+0.5*XPV
XPQ(-1)=XPQ(-1)+0.5*XPV
XPQ(2)=XPQ(2)+0.5*XPV
XPQ(-2)=XPQ(-2)+0.5*XPV
ENDIF
C...Rescale for gammaVDM by effective gamma -> rho coupling.
IF(KFA.EQ.22.AND.MINT(109).EQ.2) THEN
DO 240 KFL=-6,6
XPQ(KFL)=VINT(281)*XPQ(KFL)
240 CONTINUE
VINT(232)=VINT(281)*XPV
ENDIF
C...Isospin conjugation for neutron.
ELSEIF(KFA.EQ.2112) THEN
XPS=XPQ(1)
XPQ(1)=XPQ(2)
XPQ(2)=XPS
XPS=XPQ(-1)
XPQ(-1)=XPQ(-2)
XPQ(-2)=XPS
C...Simple recipes for hyperon (average valence structure function).
ELSEIF(KFA.EQ.3122.OR.KFA.EQ.3112.OR.KFA.EQ.3212.OR.KFA.EQ.3222
&.OR.KFA.EQ.3312.OR.KFA.EQ.3322.OR.KFA.EQ.3334) THEN
XPVAL=(XPQ(1)+XPQ(2)-XPQ(-1)-XPQ(-2))/3.
XPSEA=0.5*(XPQ(-1)+XPQ(-2))
XPQ(1)=XPSEA
XPQ(2)=XPSEA
XPQ(-1)=XPSEA
XPQ(-2)=XPSEA
XPQ(KFA/1000)=XPQ(KFA/1000)+XPVAL
XPQ(MOD(KFA/100,10))=XPQ(MOD(KFA/100,10))+XPVAL
XPQ(MOD(KFA/10,10))=XPQ(MOD(KFA/10,10))+XPVAL
ENDIF
C...Charge conjugation for antiparticle.
IF(KF.LT.0) THEN
DO 250 KFL=1,25
IF(KFL.EQ.21.OR.KFL.EQ.22.OR.KFL.EQ.23.OR.KFL.EQ.25) GOTO 250
XPS=XPQ(KFL)
XPQ(KFL)=XPQ(-KFL)
XPQ(-KFL)=XPS
250 CONTINUE
ENDIF
C...Allow gluon also in position 21.
XPQ(21)=XPQ(0)
C...Check positivity and reset above maximum allowed flavour.
DO 260 KFL=-25,25
XPQ(KFL)=MAX(0.,XPQ(KFL))
IF(IABS(KFL).GT.MSTP(58).AND.IABS(KFL).LE.8) XPQ(KFL)=0.
260 CONTINUE
C...Formats for error printouts.
5000 FORMAT(' Error: x value outside physical range; x =',1P,E12.3)
5100 FORMAT(' Error: illegal particle code for structure function;',
&' KF =',I5)
5200 FORMAT(' Error: unknown structure function; KF, library, set =',
&3I5)
RETURN
END