[u/mrichter/AliRoot.git] / HIJING / hijing1_36 / gphoton.F

* $Id$
C
C
C
	FUNCTION GPHOTON(Y1,Y2,PT2)
	IMPLICIT REAL*8 (A-H,O-Z)
#define BLANKET_SAVE
#include "hiparnt.inc"
	DIMENSION F(2,7)
	SAVE
	XT=2.0*DSQRT(PT2)/HINT1(1)
	X1=0.50*XT*(DEXP(Y1)+DEXP(Y2))
	X2=0.50*XT*(DEXP(-Y1)+DEXP(-Y2))
	Z=DSQRT(1.D0-XT**2/X1/X2)
	SS=X1*X2*HINT1(1)**2
	T=-(1.0-Z)/2.0
	U=-(1.0+Z)/2.0
	AF=3.0
	DLAM=HIPR1(15)
	APH=12.0*3.1415926/(33.0-2.0*AF)/DLOG(PT2/DLAM**2)
	APHEM=1.0/137.0
C
	CALL PARTON(F,X1,X2,PT2)
C
	G11=-(U**2+1.0)/U/3.0*F(1,7)*(4.0*F(2,1)+4.0*F(2,2)
     &      +F(2,3)+F(2,4)+F(2,5)+F(2,6))/9.0
	G12=-(T**2+1.0)/T/3.0*F(2,7)*(4.0*F(1,1)+4.0*F(1,2)
     &      +F(1,3)+F(1,4)+F(1,5)+F(1,6))/9.0
	G2=8.0*(U**2+T**2)/U/T/9.0*(4.0*F(1,1)*F(2,2)
     &     +4.0*F(1,2)*F(2,1)+F(1,3)*F(2,4)+F(1,4)*F(2,3)
     &     +F(1,5)*F(2,6)+F(1,6)*F(2,5))/9.0
C
	GPHOTON=(G11+G12+G2)*HIPR1(23)*3.14159*APH*APHEM/SS**2
	RETURN
	END
Commit	Line	Data
e74335a4	1	* $Id$
	2	C
	3	C
	4	C
	5	FUNCTION GPHOTON(Y1,Y2,PT2)
	6	IMPLICIT REAL*8 (A-H,O-Z)
bc676b8e	7	#define BLANKET_SAVE
e74335a4	8	#include "hiparnt.inc"
	9	DIMENSION F(2,7)
	10	SAVE
	11	XT=2.0*DSQRT(PT2)/HINT1(1)
	12	X1=0.50XT(DEXP(Y1)+DEXP(Y2))
	13	X2=0.50XT(DEXP(-Y1)+DEXP(-Y2))
	14	Z=DSQRT(1.D0-XT**2/X1/X2)
	15	SS=X1X2HINT1(1)**2
	16	T=-(1.0-Z)/2.0
	17	U=-(1.0+Z)/2.0
	18	AF=3.0
	19	DLAM=HIPR1(15)
	20	APH=12.03.1415926/(33.0-2.0AF)/DLOG(PT2/DLAM**2)
	21	APHEM=1.0/137.0
	22	C
	23	CALL PARTON(F,X1,X2,PT2)
	24	C
	25	G11=-(U*2+1.0)/U/3.0F(1,7)(4.0F(2,1)+4.0*F(2,2)
	26	& +F(2,3)+F(2,4)+F(2,5)+F(2,6))/9.0
	27	G12=-(T*2+1.0)/T/3.0F(2,7)(4.0F(1,1)+4.0*F(1,2)
	28	& +F(1,3)+F(1,4)+F(1,5)+F(1,6))/9.0
	29	G2=8.0(U2+T2)/U/T/9.0(4.0F(1,1)F(2,2)
	30	& +4.0F(1,2)F(2,1)+F(1,3)F(2,4)+F(1,4)F(2,3)
	31	& +F(1,5)F(2,6)+F(1,6)F(2,5))/9.0
	32	C
	33	GPHOTON=(G11+G12+G2)HIPR1(23)3.14159APHAPHEM/SS**2
	34	RETURN
	35	END