Table 2 shows the upsilon mass resolutions that are obtained for the North and South muon arms for the baseline chamber configuration, a configuration where all coarse cathode planes are replaced by fine cathode planes, and a configuration where just the coarse cathode planes at station two are replaced by fine cathode planes. The last two configurations give very similar mass resolutions for the North muon arm because the station two chamber resolution contributes twice as much to the error in the perpendicular momentum measurement as do stations one and three. Therefore, improving the station two resolution has more significant impact on the momentum resolution unless the resolution of station two is already a factor of two better than the resolution of the other two stations. For both of these configurations, the upsilon mass resolution in the North muon arm is reduced to approximately the limit due to multiple scattering and energy straggling in the absorber material in front of the tracking stations.
For the South muon arm, the mass resolution does not improve
noticeably if just station two has all fine cathodes, but it
does improve if all stations are changed to have all fine cathodes.
If fine cathode planes are put into all three stations then the mass
resolution improves from 250 MeV/c
to 220 MeV/c
.
Table 2: Upsilon mass resolutions obtained by the North and South muon
arms, with the baseline spectrometer chambers, chambers with all fine
cathodes, and all fine cathodes just in station 2.