Investigation of Momentum Resolution in Straight vs Bent Large End-Cap Chambers

We report on a calculation of momentum resolution for muons incident on the large end-cap chambers. The impact on the resolution of two chamber designs was evaluated: Those constructed with straight drift tubes are compared to the ATLAS baseline design in which chambers are bent such that tube axes conform to the catenary of their respective anode wires. The analysis was performed using the GARFIELD program to calculate drift tube time-to-space functions. ATLAS muon system code packages LHCTOR and MUONBOX were used to generate tracks, hits and momentum reconstruction. We find that, for straight tube chambers compared to bent ones, the overall degradation in momentum resolution, averaged over all of the largest of the so called large end-cap chambers (EML4-5 and EOL3 in the pseudo-rapidity range$1.02 < \eta <1.49$), is very small for muon transverse momentum $P_t = 500 $ Gev and negligible for $P_t \le 100 $ Gev. When the intermediate large end-cap chambers (EEL1 and EEL2) are considered no momentum degradation at $P_t= 500 $ Gev is observed.