hijing/src/pyhiw1au.f

0001
0002 C***********************************************************************
0003
0004       FUNCTION PYHIW1AU(EPS,IREIM)
0005
0006 C...Calculates real and imaginary parts of the auxiliary function W1;
0007 C...see R. K. Ellis, I. Hinchliffe, M. Soldate and J. J. van der Bij,
0008 C...FERMILAB-Pub-87/100-T, LBL-23504, June, 1987
0009       COMMON/LUDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
0010       SAVE /LUDAT1/
0011
0012       ASINH(X)=LOG(X+SQRT(X**2+1.))
0013       ACOSH(X)=LOG(X+SQRT(X**2-1.))
0014
0015       IF(EPS.LT.0.) THEN
0016         W1RE=2.*SQRT(1.-EPS)*ASINH(SQRT(-1./EPS))
0017         W1IM=0.
0018       ELSEIF(EPS.LT.1.) THEN
0019         W1RE=2.*SQRT(1.-EPS)*ACOSH(SQRT(1./EPS))
0020         W1IM=-PARU(1)*SQRT(1.-EPS)
0021       ELSE
0022         W1RE=2.*SQRT(EPS-1.)*ASIN(SQRT(1./EPS))
0023         W1IM=0.
0024       ENDIF
0025
0026       IF(IREIM.EQ.1) PYHIW1AU=W1RE
0027       IF(IREIM.EQ.2) PYHIW1AU=W1IM
0028
0029       RETURN
0030       END