pygdir.F

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       SUBROUTINE pygdir(X,Q2,P2,AK0,XPGA)
c...purpose: to evaluate the direct contribution, i.e. the c^gamma term,
c...as needed in msbar parametrizations.
      dimension xpga(-6:6)
      DATA pmc/1.3/, pmb/4.6/, aem2pi/0.0011614/
 
c...reset output.
      DO 100 kfl=-6,6
      xpga(kfl)=0.
  100 CONTINUE
 
c...evaluate common x-dependent expression.
      xtmp = (x**2+(1.-x)**2) * (-log(x)) - 1.
      cgam = 3.*aem2pi*x * (xtmp*(1.+p2/(p2+ak0**2)) + 6.*x*(1.-x))
 
c...d, u, s part by simple charge factor.
      xpga(1)=(1./9.)*cgam
      xpga(2)=(4./9.)*cgam
      xpga(3)=(1./9.)*cgam
 
c...also fill for antiquarks.
      DO 110 kf=1,5
      xpga(-kf)=xpga(kf)
  110 CONTINUE
 
      RETURN
      END