)
Figure 9:
Azimuthal angular distributions measured for 6< r < 7cm at z=+1m
for vertical displacements of =
(solid line), 
(dotted line)
compared with the nominal one (solid circles). The distributions are
normalized by the total number of particles.
When two beams collide with a finite vertical
displacement() comparable to 
, we expect a
vertical, i.e. up-down, asymmetry in the azimuthal angular
distribution. In the simulation beam-1 and beam-2 are initially
shifted by 
and 
, respectively. We
examined the two cases of 
and , and plotted the angular distribution in
Fig.9. (The luminosity losses are 6 and 30% for
and ,
respectively.) Apparently, during a collision the particles are
deflected more in the upper side of the electromagnetic field of
beam-2, since they are created in the overlapping region between two
beams. Therefore, they are deflected more in +y and less in -y
than in the nominal case, as can be clearly seen in
Fig.9. The ratios 
are found to be 0.76 and
0.62 for =
0.5 and
1, respectively.