hijing/src/pyhiw2au.f

0001
0002 C***********************************************************************
0003
0004       FUNCTION PYHIW2AU(EPS,IREIM)
0005
0006 C...Calculates real and imaginary parts of the auxiliary function W2;
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         W2RE=4.*(ASINH(SQRT(-1./EPS)))**2
0017         W2IM=0.
0018       ELSEIF(EPS.LT.1.) THEN
0019         W2RE=4.*(ACOSH(SQRT(1./EPS)))**2-PARU(1)**2
0020         W2IM=-4.*PARU(1)*ACOSH(SQRT(1./EPS))
0021       ELSE
0022         W2RE=-4.*(ASIN(SQRT(1./EPS)))**2
0023         W2IM=0.
0024       ENDIF
0025
0026       IF(IREIM.EQ.1) PYHIW2AU=W2RE
0027       IF(IREIM.EQ.2) PYHIW2AU=W2IM
0028
0029       RETURN
0030       END