RPC and DTBX Trigger Capability

First we looked how efficient the generated single muons are reconstructed by the RPC and DTBX trigger systems with respect to their kinematical variables , and . In fig. 2 we plot the ratio of reconstructed to generated tracks as a function these variables.

  
Figure 2: Trigger efficiencies for RPC and DTBX as functions of , and . The full line represents the DTBX efficiencies and the dashed line the RPC efficiencies.

Obviously in the regions of and both RPC and DTBX show inefficiencies. Geometrically this corresponds to crack positions, where two wheels carrying RPC and DTBX chambers are fitted together. For > 0.8 a rather different behaviour for DTBX and RPC is observable. In this regime obviously the overlap region to the forward muon system starts to be important especially for the DTBX system, since no CSC information was included in this study.

Similarly we find inefficiencies in , which appear every 30 degrees reflecting the setup of the detector planes.

On the other hand we do not observe a strong dependence of the trigger efficiency. DTBX has a slightly higher trigger efficiency compared to RPC, but has clearly losses in the low- region < 10 GeV/c. Therefore in fig. 3 the dependence of the efficiency is separately plotted for our small sample of low muons.

To put our analysis of both trigger systems on a comparable footing we restrict our analysis to the region of < 0.8.

In table 3 we calculated the overall capability of the two trigger systems to reconstruct muons in this restricted regime. RPC will find in 95.5% and DTBX in 93.2% of the cases one muon from one generated, but for 4.5% and 3.6% of the tracks the reconstruction fails.

More than one muon (e.g. ghost tracks) are found by RPC in 0.02% of the generated single muon events, but by DTBX with a much higher percentage of 3.3%, which is a reflection of the left/right ambiguity of the DTBX system and needs careful investigation to avoid problems at higher muon multiplicities.

  
Figure 3: Trigger efficiency for low muons vs. . The full line represents the DTBX efficiency and the dashed line the RPC efficiency.

  
Table 3: Trigger efficiencies for single muons.

The charge of the generated muons is incorrectly reconstructed in about 4% of the cases for both RPC and DTBX. The probability for such misassignments increases with higher and can be attributed to reconstruction problems. This occurs in the critical (i.e. less efficient) regions (1., 0.75, 0.2), where the input spectra get distorted during reconstruction. Either the reconstructed transverse momenta for muons with a wrong charge assigned are very low ( < 30 GeV/c) for DTBX or very (100 GeV/c) for the RPC.