pyhii3au.f

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C***********************************************************************    
    
      FUNCTION pyhii3au(BE,EPS,IREIM) 
    
C...Calculates real and imaginary parts of the auxiliary function I3;   
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/ 
    
      IF(eps.LT.1.) ga=0.5*(1.+sqrt(1.-eps))    
    
      IF(eps.LT.0.) THEN    
        f3re=pyhispen((ga-1.)/(ga+be-1.),0.,1)-
     &  pyhispen(ga/(ga+be-1.),0.,1)+    
     &  pyhispen((be-ga)/be,0.,1)-pyhispen((be-ga)/(be-1.),0.,1)+   
     &  (log(be)**2-log(be-1.)**2)/2.+log(ga)*log((ga+be-1.)/be)+   
     &  log(ga-1.)*log((be-1.)/(ga+be-1.))  
        f3im=0. 
      ELSEIF(eps.LT.1.) THEN    
        f3re=pyhispen((ga-1.)/(ga+be-1.),0.,1)-
     &  pyhispen(ga/(ga+be-1.),0.,1)+    
     &  pyhispen(ga/(ga-be),0.,1)-pyhispen((ga-1.)/(ga-be),0.,1)+   
     &  log(ga/(1.-ga))*log((ga+be-1.)/(be-ga)) 
        f3im=-paru(1)*log((ga+be-1.)/(be-ga))   
      ELSE  
        rsq=eps/(eps-1.+(2.*be-1.)**2)  
        rcthe=rsq*(1.-2.*be/eps)    
        rsthe=sqrt(rsq-rcthe**2)    
        rcphi=rsq*(1.+2.*(be-1.)/eps)   
        rsphi=sqrt(rsq-rcphi**2)    
        r=sqrt(rsq) 
        the=acos(rcthe/r)   
        phi=acos(rcphi/r)   
        f3re=pyhispen(rcthe,rsthe,1)+pyhispen(rcthe,-rsthe,1)-  
     &  pyhispen(rcphi,rsphi,1)-pyhispen(rcphi,-rsphi,1)+   
     &  (phi-the)*(phi+the-paru(1)) 
        f3im=pyhispen(rcthe,rsthe,2)+pyhispen(rcthe,-rsthe,2)-  
     &  pyhispen(rcphi,rsphi,2)-pyhispen(rcphi,-rsphi,2)    
      ENDIF 
    
      IF(ireim.EQ.1) pyhii3au=2./(2.*be-1.)*f3re  
      IF(ireim.EQ.2) pyhii3au=2./(2.*be-1.)*f3im  
    
      RETURN    
      END