  The beams at the ILC produce electron positron pairs due to beam-beam
interactions. This note presents for the first time a study of these processes
in a detailed simulation, which shows that these pair background particles
appear at angles that extend to the inner layers of the detector. The full data
set of pairs produced in one bunch crossing was used to calculate the helix
tracks, which the particles form in the solenoid field of the SiD detector. The
results suggest to further study the reduction of the beam pipe radius and
therefore to either add another SiD vertex detector layer, or reduce the radius
of the existing vertex detector layers, without increasing the detector
occupancy significantly. This has to go along with additional studies whether
the improvement in physics reconstruction methods, like c-tagging, is worth the
increased background level at smaller radii.
