hijing/src/g.f

0001 C
0002 C
0003 C
0004 C
0005         FUNCTION G(Y1,Y2,PT2)
0006         IMPLICIT REAL*8 (A-H,O-Z)
0007         REAL HIPR1(100),HINT1(100)
0008         COMMON/HIPARNT/HIPR1,IHPR2(50),HINT1,IHNT2(50)
0009         SAVE  /HIPARNT/
0010         DIMENSION F(2,7)
0011         XT=2.0*DSQRT(PT2)/HINT1(1)
0012         X1=0.50*XT*(DEXP(Y1)+DEXP(Y2))
0013         X2=0.50*XT*(DEXP(-Y1)+DEXP(-Y2))
0014         Z=DSQRT(1.D0-XT**2/X1/X2)
0015         SS=X1*X2*HINT1(1)**2
0016         T=-(1.0-Z)/2.0
0017         U=-(1.0+Z)/2.0
0018         AF=3.0
0019         DLAM=HIPR1(15)
0020         APH=12.0*3.1415926/(33.0-2.0*AF)/DLOG(PT2/DLAM**2)
0021 C
0022         CALL PARTON(F,X1,X2,PT2)
0023 C
0024         G11=( (F(1,1)+F(1,2))*(F(2,3)+F(2,4)+F(2,5)+F(2,6))
0025      &      +(F(1,3)+F(1,4))*(F(2,5)+F(2,6)) )*SUBCRS1(T,U)
0026 C
0027         G12=( (F(2,1)+F(2,2))*(F(1,3)+F(1,4)+F(1,5)+F(1,6))
0028      &      +(F(2,3)+F(2,4))*(F(1,5)+F(1,6)) )*SUBCRS1(U,T)
0029 C
0030         G13=(F(1,1)*F(2,1)+F(1,2)*F(2,2)+F(1,3)*F(2,3)+F(1,4)*F(2,4)
0031      &      +F(1,5)*F(2,5)+F(1,6)*F(2,6))*(SUBCRS1(U,T)
0032      &      +SUBCRS1(T,U)-8.D0/T/U/27.D0)
0033 C
0034         G2=(AF-1)*(F(1,1)*F(2,2)+F(2,1)*F(1,2)+F(1,3)*F(2,4)
0035      &     +F(2,3)*F(1,4)+F(1,5)*F(2,6)+F(2,5)*F(1,6))*SUBCRS2(T,U)
0036 C
0037         G31=(F(1,1)*F(2,2)+F(1,3)*F(2,4)+F(1,5)*F(2,6))*SUBCRS3(T,U)
0038         G32=(F(2,1)*F(1,2)+F(2,3)*F(1,4)+F(2,5)*F(1,6))*SUBCRS3(U,T)
0039 C
0040         G4=(F(1,1)*F(2,2)+F(2,1)*F(1,2)+F(1,3)*F(2,4)+F(2,3)*F(1,4)+
0041      1  F(1,5)*F(2,6)+F(2,5)*F(1,6))*SUBCRS4(T,U)
0042 C
0043         G5=AF*F(1,7)*F(2,7)*SUBCRS5(T,U)
0044 C
0045         G61=F(1,7)*(F(2,1)+F(2,2)+F(2,3)+F(2,4)+F(2,5)
0046      &      +F(2,6))*SUBCRS6(T,U)
0047         G62=F(2,7)*(F(1,1)+F(1,2)+F(1,3)+F(1,4)+F(1,5)
0048      &      +F(1,6))*SUBCRS6(U,T)
0049 C
0050         G7=F(1,7)*F(2,7)*SUBCRS7(T,U)
0051 C
0052         G=(G11+G12+G13+G2+G31+G32+G4+G5+G61+G62+G7)*HIPR1(17)*
0053      1  3.14159D0*APH**2/SS**2
0054
0055         RETURN
0056         END