pywaux.f

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C***********************************************************************
 
C...PYWAUX
C...Calculates real and imaginary parts of the auxiliary functions W1
C...and W2; see R. K. Ellis, I. Hinchliffe, M. Soldate and J. J. van
C...der Bij, Nucl. Phys. B297 (1988) 221.
 
      SUBROUTINE pywaux(IAUX,EPS,WRE,WIM)
 
C...Double precision and integer declarations.
      IMPLICIT DOUBLE PRECISION(a-h, o-z)
      IMPLICIT INTEGER(i-n)
      INTEGER pyk,pychge,pycomp
C...Commonblocks.
      common/pydat1/mstu(200),paru(200),mstj(200),parj(200)
      SAVE /pydat1/
 
      asinh(x)=log(x+sqrt(x**2+1d0))
      acosh(x)=log(x+sqrt(x**2-1d0))
 
      IF(eps.LT.0d0) THEN
        IF(iaux.EQ.1) wre=2d0*sqrt(1d0-eps)*asinh(sqrt(-1d0/eps))
        IF(iaux.EQ.2) wre=4d0*(asinh(sqrt(-1d0/eps)))**2
        wim=0d0
      ELSEIF(eps.LT.1d0) THEN
        IF(iaux.EQ.1) wre=2d0*sqrt(1d0-eps)*acosh(sqrt(1d0/eps))
        IF(iaux.EQ.2) wre=4d0*(acosh(sqrt(1d0/eps)))**2-paru(1)**2
        IF(iaux.EQ.1) wim=-paru(1)*sqrt(1d0-eps)
        IF(iaux.EQ.2) wim=-4d0*paru(1)*acosh(sqrt(1d0/eps))
      ELSE
        IF(iaux.EQ.1) wre=2d0*sqrt(eps-1d0)*asin(sqrt(1d0/eps))
        IF(iaux.EQ.2) wre=-4d0*(asin(sqrt(1d0/eps)))**2
        wim=0d0
      ENDIF
 
      RETURN
      END