HIJING/hipyset1_35/pyi3au_hijing.F

   1 * $Id$
   2
   3 C***********************************************************************
   4
   5       FUNCTION PYI3AU_HIJING(BE,EPS,IREIM)
   6
   7 C...Calculates real and imaginary parts of the auxiliary function I3;
   8 C...see R. K. Ellis, I. Hinchliffe, M. Soldate and J. J. van der Bij,
   9 C...FERMILAB-Pub-87/100-T, LBL-23504, June, 1987
  10 #include "ludat1_hijing.inc"
  11
  12       IF(EPS.LT.1.) GA=0.5*(1.+SQRT(1.-EPS))
  13
  14       IF(EPS.LT.0.) THEN
  15          F3RE=PYSPEN_HIJING((GA-1.)/(GA+BE-1.),0.,1)-PYSPEN_HIJING(GA
  16      $        /(GA+BE-1.),0.,1)+PYSPEN_HIJING((BE-GA)/BE,0.,1)
  17      $        -PYSPEN_HIJING((BE-GA)/(BE-1.),0.,1)+(LOG(BE)**2-LOG(BE-1.
  18      $        )**2)/2.+LOG(GA)*LOG((GA+BE-1.)/BE)+LOG(GA-1.)*LOG((BE-1.)
  19      $        /(GA+BE-1.))
  20         F3IM=0.
  21       ELSEIF(EPS.LT.1.) THEN
  22          F3RE=PYSPEN_HIJING((GA-1.)/(GA+BE-1.),0.,1)-PYSPEN_HIJING(GA
  23      $        /(GA+BE-1.),0.,1)+PYSPEN_HIJING(GA/(GA-BE),0.,1)
  24      $        -PYSPEN_HIJING((GA-1.)/(GA-BE),0.,1)+LOG(GA/(1.-GA))
  25      $        *LOG((GA+BE-1.)/(BE-GA))
  26         F3IM=-PARU(1)*LOG((GA+BE-1.)/(BE-GA))
  27       ELSE
  28         RSQ=EPS/(EPS-1.+(2.*BE-1.)**2)
  29         RCTHE=RSQ*(1.-2.*BE/EPS)
  30         RSTHE=SQRT(RSQ-RCTHE**2)
  31         RCPHI=RSQ*(1.+2.*(BE-1.)/EPS)
  32         RSPHI=SQRT(RSQ-RCPHI**2)
  33         R=SQRT(RSQ)
  34         THE=ACOS(RCTHE/R)
  35         PHI=ACOS(RCPHI/R)
  36         F3RE=PYSPEN_HIJING(RCTHE,RSTHE,1)+PYSPEN_HIJING(RCTHE,-RSTHE,1)-
  37      &  PYSPEN_HIJING(RCPHI,RSPHI,1)-PYSPEN_HIJING(RCPHI,-RSPHI,1)+
  38      &  (PHI-THE)*(PHI+THE-PARU(1))
  39         F3IM=PYSPEN_HIJING(RCTHE,RSTHE,2)+PYSPEN_HIJING(RCTHE,-RSTHE,2)-
  40      &  PYSPEN_HIJING(RCPHI,RSPHI,2)-PYSPEN_HIJING(RCPHI,-RSPHI,2)
  41       ENDIF
  42
  43       IF(IREIM.EQ.1) PYI3AU_HIJING=2./(2.*BE-1.)*F3RE
  44       IF(IREIM.EQ.2) PYI3AU_HIJING=2./(2.*BE-1.)*F3IM
  45
  46       RETURN
  47       END