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pyhiw2au.f
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1 
2 C***********************************************************************
3 
4  FUNCTION pyhiw2au(EPS,IREIM)
5 
6 C...Calculates real and imaginary parts of the auxiliary function W2;
7 C...see R. K. Ellis, I. Hinchliffe, M. Soldate and J. J. van der Bij,
8 C...FERMILAB-Pub-87/100-T, LBL-23504, June, 1987
9  common/ludat1/mstu(200),paru(200),mstj(200),parj(200)
10  SAVE /ludat1/
11 
12  asinh(x)=log(x+sqrt(x**2+1.))
13  acosh(x)=log(x+sqrt(x**2-1.))
14 
15  IF(eps.LT.0.) THEN
16  w2re=4.*(asinh(sqrt(-1./eps)))**2
17  w2im=0.
18  ELSEIF(eps.LT.1.) THEN
19  w2re=4.*(acosh(sqrt(1./eps)))**2-paru(1)**2
20  w2im=-4.*paru(1)*acosh(sqrt(1./eps))
21  ELSE
22  w2re=-4.*(asin(sqrt(1./eps)))**2
23  w2im=0.
24  ENDIF
25 
26  IF(ireim.EQ.1) pyhiw2au=w2re
27  IF(ireim.EQ.2) pyhiw2au=w2im
28 
29  RETURN
30  END