Table 1 shows the contributions to
the upsilon mass resolution
for the North and South muon arms. The contribution from
the multiple scattering and energy straggling in the material
in front of the tracking stations was determined by using the
true momentum vector at the first tracking station and tracking
back to the vertex. If the tracking stations are then given
perfect resolution, but the particle is tracked all the way from
the last tracking station to the vertex, then the limit from
the multiple scattering in both the material in front of the
tracking stations as well as the air and chamber material
in the tracking volume is obtained. Lastly, the expected
finite chamber resolution was added to the simulation
to give the mass resolution when all material and detector
resolutions are taken into account. The expected resolution
is 100 
m per fine resolution plane and three fine resolution
planes per station.
Table 1: Upsilon mass resolutions obtained by the North and South muon
arms, with a perfect spectrometer (no material and perfect resolution),
with material added but still perfect chamber resolutions, and with
chamber resolutions added.
The North muon arm upsilon mass resolution is limited to
180 MeV/c
by the multiple scattering and energy straggling
in the material in front of the tracking stations. The South
arm is limited to only 148 MeV/c
because of the shorter
nosecone. However, because the lever arm is significantly
shorter in the South arm than in the North arm the
sagitta (or kick) is significantly smaller in the South arm than in the
North arm for the same momentum particle. This means that the chamber
resolutions and multiple scattering in the spectrometer material
more strongly affect the momentum resolution in the South arm than
in the North arm.
The shorter length of air causing multiple scattering only
slightly compensates for this. The result is that the multiple
scattering in the air and chamber material in the South arm increases
the upsilon mass resolution from 148 MeV/c
to 180 MeV/c
while leaving the mass resolution in the North arm relatively
unchanged. The baseline chamber resolutions further degrade the
upsilon mass resolution in the South arm to 250 MeV/c
while
degrading the North arm resolution to only 205 MeV/c
. Because
the chamber resolution is still contributing to the upsilon mass
resolution in both arms, we have investigated improving the
chamber resolution by changing the number of fine cathode planes
in each station. This is presented in the next section.