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.