This commit was generated by cvs2svn to compensate for changes in r1073,

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

diff --git a/HIJING/hijing1_36/gphoton.F b/HIJING/hijing1_36/gphoton.F
new file mode 100644 (file)
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+++ b/HIJING/hijing1_36/gphoton.F
@@ -0,0 +1,34 @@
+* $Id$
+C
+C
+C
+       FUNCTION GPHOTON(Y1,Y2,PT2)
+       IMPLICIT REAL*8 (A-H,O-Z)
+#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