pygrvs.f

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C*********************************************************************
 
C...PYGRVS
C...Auxiliary for the GRV 94 parton distribution functions
C...for s, c and b sea.
C...Authors: M. Glueck, E. Reya and A. Vogt.
 
      FUNCTION pygrvs (X, S, STH, AL, BE, AK, AG, B, D, E, ES)
 
C...Double precision declaration.
      IMPLICIT DOUBLE PRECISION (a - z)
 
C...Evaluation.
      IF(s.LE.sth) THEN
        pygrvs = 0d0
      ELSE
        dx = sqrt(x)
        lx = log(1d0/x)
        pygrvs = (s - sth)**al / lx**ak * (1d0+ ag*dx + b*x) *
     &     (1d0- x)**d * exp(-e + sqrt(es * s**be * lx))
      ENDIF
 
      RETURN
      END