X-Git-Url: http://git.uio.no/git/?p=u%2Fmrichter%2FAliRoot.git;a=blobdiff_plain;f=HERWIG%2Fjimmy%2Fjimmy%2Fjmarea.F;fp=HERWIG%2Fjimmy%2Fjimmy%2Fjmarea.F;h=c50bf7e86f92c99a5ed79957995f388d060137ba;hp=0000000000000000000000000000000000000000;hb=ef94df367b991ca790f9d51da7f31bd7560e2cbe;hpb=657679557603e320230da5df469d688018515c79

diff --git a/HERWIG/jimmy/jimmy/jmarea.F b/HERWIG/jimmy/jimmy/jmarea.F
new file mode 100644
index 00000000000..c50bf7e86f9
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+++ b/HERWIG/jimmy/jimmy/jmarea.F
@@ -0,0 +1,59 @@
+      DOUBLE PRECISION FUNCTION JMAREA( B2 )
+c ----------------------------------------------------------------------
+c   Purpose: Returns area overlap A(B)
+c      Mods: 20-Aug-1993 JMB. Allow use of CERNLIB.
+c      Mods: 27-Jan-1995  RW. Allow e+e- (not NAGLIB!)
+c ----------------------------------------------------------------------
+
+#include "herwig65.inc"
+#include "jimmy.inc"
+
+      INTEGER NPHOTONS
+      DOUBLE PRECISION B2,AREA
+      DOUBLE PRECISION JMDBESK0, JMDBESK1, BESSEL(0:3)
+      DOUBLE PRECISION X1, X2
+
+      IF (B2.LE.0.D0) THEN
+        IF (JMBUG.GT.11) WRITE(JMOUT,*)'**** JMAREA:B2=',B2
+        JMAREA = 0.D0
+        RETURN
+      ENDIF
+      X1=(JMV2*B2)**.5
+      X2=(JMU2*B2)**.5
+
+      NPHOTONS=0
+      IF ((ABS(IDPDG(IPART1)).EQ.11).OR.(ABS(IDPDG(IPART1)).EQ.22))
+     $     NPHOTONS=NPHOTONS+1
+      IF ((ABS(IDPDG(IPART2)).EQ.11).OR.(ABS(IDPDG(IPART2)).EQ.22))
+     $     NPHOTONS=NPHOTONS+1
+
+      IF (NPHOTONS.EQ.1) THEN
+C     `ep' type run
+C     Modified Bessel function K0
+         AREA = JMDBESK0(X1)
+         AREA = (AREA-JMDBESK0(X2))*JMU2/(JMU2-JMV2)
+
+C       Modified Bessel function K1
+         AREA=(AREA-X2/TWO*JMDBESK1(X2))*JMU2*JMV2/(JMU2-JMV2)/
+     &        (TWO*PIFAC)
+         
+      ELSE IF (NPHOTONS.EQ.2) THEN
+         
+C     `e+e-' type run.
+C     Modified Bessel function K1
+         AREA = JMV2*X1*JMDBESK1(X1)/(4.D0*PIFAC)
+         
+         
+      ELSE IF (NPHOTONS.EQ.0) THEN
+         
+C     `pp' type run.
+C     Modified Bessel function K3
+         CALL JMDBSKA(X2,0,1,3,BESSEL)
+         AREA = JMU2/96/PIFAC*(X2**3)*BESSEL(3)
+         
+      ENDIF
+
+      JMAREA = AREA
+
+      RETURN
+      END