--- /dev/null
+
+C*********************************************************************
+
+ SUBROUTINE PYSTPI(X,Q2,XPPI)
+
+C...Gives pi+ structure function according to two different
+C...parametrizations.
+ COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
+ COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
+ COMMON/PYINT1/MINT(400),VINT(400)
+ SAVE /LUDAT1/
+ SAVE /PYPARS/,/PYINT1/
+ DIMENSION XPPI(-6:6),COW(3,5,4,2),XQ(9),TS(6)
+
+C...The following data lines are coefficients needed in the
+C...Owens pion structure function parametrizations, see below.
+C...Expansion coefficients for up and down valence quark distributions.
+ DATA ((COW(IP,IS,1,1),IS=1,5),IP=1,3)/
+ 1 4.0000E-01, 7.0000E-01, 0.0000E+00, 0.0000E+00, 0.0000E+00,
+ 2 -6.2120E-02, 6.4780E-01, 0.0000E+00, 0.0000E+00, 0.0000E+00,
+ 3 -7.1090E-03, 1.3350E-02, 0.0000E+00, 0.0000E+00, 0.0000E+00/
+ DATA ((COW(IP,IS,1,2),IS=1,5),IP=1,3)/
+ 1 4.0000E-01, 6.2800E-01, 0.0000E+00, 0.0000E+00, 0.0000E+00,
+ 2 -5.9090E-02, 6.4360E-01, 0.0000E+00, 0.0000E+00, 0.0000E+00,
+ 3 -6.5240E-03, 1.4510E-02, 0.0000E+00, 0.0000E+00, 0.0000E+00/
+C...Expansion coefficients for gluon distribution.
+ DATA ((COW(IP,IS,2,1),IS=1,5),IP=1,3)/
+ 1 8.8800E-01, 0.0000E+00, 3.1100E+00, 6.0000E+00, 0.0000E+00,
+ 2 -1.8020E+00, -1.5760E+00, -1.3170E-01, 2.8010E+00, -1.7280E+01,
+ 3 1.8120E+00, 1.2000E+00, 5.0680E-01, -1.2160E+01, 2.0490E+01/
+ DATA ((COW(IP,IS,2,2),IS=1,5),IP=1,3)/
+ 1 7.9400E-01, 0.0000E+00, 2.8900E+00, 6.0000E+00, 0.0000E+00,
+ 2 -9.1440E-01, -1.2370E+00, 5.9660E-01, -3.6710E+00, -8.1910E+00,
+ 3 5.9660E-01, 6.5820E-01, -2.5500E-01, -2.3040E+00, 7.7580E+00/
+C...Expansion coefficients for (up+down+strange) quark sea distribution.
+ DATA ((COW(IP,IS,3,1),IS=1,5),IP=1,3)/
+ 1 9.0000E-01, 0.0000E+00, 5.0000E+00, 0.0000E+00, 0.0000E+00,
+ 2 -2.4280E-01, -2.1200E-01, 8.6730E-01, 1.2660E+00, 2.3820E+00,
+ 3 1.3860E-01, 3.6710E-03, 4.7470E-02, -2.2150E+00, 3.4820E-01/
+ DATA ((COW(IP,IS,3,2),IS=1,5),IP=1,3)/
+ 1 9.0000E-01, 0.0000E+00, 5.0000E+00, 0.0000E+00, 0.0000E+00,
+ 2 -1.4170E-01, -1.6970E-01, -2.4740E+00, -2.5340E+00, 5.6210E-01,
+ 3 -1.7400E-01, -9.6230E-02, 1.5750E+00, 1.3780E+00, -2.7010E-01/
+C...Expansion coefficients for charm quark sea distribution.
+ DATA ((COW(IP,IS,4,1),IS=1,5),IP=1,3)/
+ 1 0.0000E+00, -2.2120E-02, 2.8940E+00, 0.0000E+00, 0.0000E+00,
+ 2 7.9280E-02, -3.7850E-01, 9.4330E+00, 5.2480E+00, 8.3880E+00,
+ 3 -6.1340E-02, -1.0880E-01, -1.0852E+01, -7.1870E+00, -1.1610E+01/
+ DATA ((COW(IP,IS,4,2),IS=1,5),IP=1,3)/
+ 1 0.0000E+00, -8.8200E-02, 1.9240E+00, 0.0000E+00, 0.0000E+00,
+ 2 6.2290E-02, -2.8920E-01, 2.4240E-01, -4.4630E+00, -8.3670E-01,
+ 3 -4.0990E-02, -1.0820E-01, 2.0360E+00, 5.2090E+00, -4.8400E-02/
+
+C...Euler's beta function, requires ordinary Gamma function
+ EULBET(X,Y)=PYGAMM(X)*PYGAMM(Y)/PYGAMM(X+Y)
+
+C...Reset output array.
+ DO 100 KFL=-6,6
+ XPPI(KFL)=0.
+ 100 CONTINUE
+
+ IF(MSTP(53).LE.2) THEN
+C...Pion structure functions from Owens.
+C...Allowed variable range: 4 GeV^2 < Q^2 < approx 2000 GeV^2.
+
+C...Determine set, Lambda and s expansion variable.
+ NSET=MSTP(53)
+ IF(NSET.EQ.1) ALAM=0.2
+ IF(NSET.EQ.2) ALAM=0.4
+ VINT(231)=4.
+ IF(MSTP(57).LE.0) THEN
+ SD=0.
+ ELSE
+ Q2IN=MIN(2E3,MAX(4.,Q2))
+ SD=LOG(LOG(Q2IN/ALAM**2)/LOG(4./ALAM**2))
+ ENDIF
+
+C...Calculate structure functions.
+ DO 120 KFL=1,4
+ DO 110 IS=1,5
+ TS(IS)=COW(1,IS,KFL,NSET)+COW(2,IS,KFL,NSET)*SD+
+ & COW(3,IS,KFL,NSET)*SD**2
+ 110 CONTINUE
+ IF(KFL.EQ.1) THEN
+ XQ(KFL)=X**TS(1)*(1.-X)**TS(2)/EULBET(TS(1),TS(2)+1.)
+ ELSE
+ XQ(KFL)=TS(1)*X**TS(2)*(1.-X)**TS(3)*(1.+TS(4)*X+TS(5)*X**2)
+ ENDIF
+ 120 CONTINUE
+
+C...Put into output array.
+ XPPI(0)=XQ(2)
+ XPPI(1)=XQ(3)/6.
+ XPPI(2)=XQ(1)+XQ(3)/6.
+ XPPI(3)=XQ(3)/6.
+ XPPI(4)=XQ(4)
+ XPPI(-1)=XQ(1)+XQ(3)/6.
+ XPPI(-2)=XQ(3)/6.
+ XPPI(-3)=XQ(3)/6.
+ XPPI(-4)=XQ(4)
+
+C...Leading order pion structure functions from Gluck, Reya and Vogt.
+C...Allowed variable range: 0.25 GeV^2 < Q^2 < 10^8 GeV^2 and
+C...10^-5 < x < 1.
+ ELSE
+
+C...Determine s expansion variable and some x expressions.
+ VINT(231)=0.25
+ IF(MSTP(57).LE.0) THEN
+ SD=0.
+ ELSE
+ Q2IN=MIN(1E8,MAX(0.25,Q2))
+ SD=LOG(LOG(Q2IN/0.232**2)/LOG(0.25/0.232**2))
+ ENDIF
+ SD2=SD**2
+ XL=-LOG(X)
+ XS=SQRT(X)
+
+C...Evaluate valence, gluon and sea distributions.
+ XFVAL=(0.519+0.180*SD-0.011*SD2)*X**(0.499-0.027*SD)*
+ & (1.+(0.381-0.419*SD)*XS)*(1.-X)**(0.367+0.563*SD)
+ XFGLU=(X**(0.482+0.341*SQRT(SD))*((0.678+0.877*SD-0.175*SD2)+
+ & (0.338-1.597*SD)*XS+(-0.233*SD+0.406*SD2)*X)+
+ & SD**0.599*EXP(-(0.618+2.070*SD)+SQRT(3.676*SD**1.263*XL)))*
+ & (1.-X)**(0.390+1.053*SD)
+ XFSEA=SD**0.55*(1.-0.748*XS+(0.313+0.935*SD)*X)*(1.-X)**3.359*
+ & EXP(-(4.433+1.301*SD)+SQRT((9.30-0.887*SD)*SD**0.56*XL))/
+ & XL**(2.538-0.763*SD)
+ IF(SD.LE.0.888) THEN
+ XFCHM=0.
+ ELSE
+ XFCHM=(SD-0.888)**1.02*(1.+1.008*X)*(1.-X)**(1.208+0.771*SD)*
+ & EXP(-(4.40+1.493*SD)+SQRT((2.032+1.901*SD)*SD**0.39*XL))
+ ENDIF
+ IF(SD.LE.1.351) THEN
+ XFBOT=0.
+ ELSE
+ XFBOT=(SD-1.351)**1.03*(1.-X)**(0.697+0.855*SD)*
+ & EXP(-(4.51+1.490*SD)+SQRT((3.056+1.694*SD)*SD**0.39*XL))
+ ENDIF
+
+C...Put into output array.
+ XPPI(0)=XFGLU
+ XPPI(1)=XFSEA
+ XPPI(2)=XFSEA
+ XPPI(3)=XFSEA
+ XPPI(4)=XFCHM
+ XPPI(5)=XFBOT
+ DO 130 KFL=1,5
+ XPPI(-KFL)=XPPI(KFL)
+ 130 CONTINUE
+ XPPI(2)=XPPI(2)+XFVAL
+ XPPI(-1)=XPPI(-1)+XFVAL
+ ENDIF
+
+ RETURN
+ END
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff