pyhiw1au.f

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C***********************************************************************    
    
      FUNCTION pyhiw1au(EPS,IREIM)    
    
C...Calculates real and imaginary parts of the auxiliary function W1;   
C...see R. K. Ellis, I. Hinchliffe, M. Soldate and J. J. van der Bij,   
C...FERMILAB-Pub-87/100-T, LBL-23504, June, 1987    
      common/ludat1/mstu(200),paru(200),mstj(200),parj(200) 
      SAVE /ludat1/ 
    
      asinh(x)=log(x+sqrt(x**2+1.)) 
      acosh(x)=log(x+sqrt(x**2-1.)) 
    
      IF(eps.LT.0.) THEN    
        w1re=2.*sqrt(1.-eps)*asinh(sqrt(-1./eps))   
        w1im=0. 
      ELSEIF(eps.LT.1.) THEN    
        w1re=2.*sqrt(1.-eps)*acosh(sqrt(1./eps))    
        w1im=-paru(1)*sqrt(1.-eps)  
      ELSE  
        w1re=2.*sqrt(eps-1.)*asin(sqrt(1./eps)) 
        w1im=0. 
      ENDIF 
    
      IF(ireim.EQ.1) pyhiw1au=w1re    
      IF(ireim.EQ.2) pyhiw1au=w1im    
    
      RETURN    
      END