Setup of a Drift Tube Muon Tracker and Calibration of Muon ...

Hits per Event - Plane 0N1000h_hit0Entries 2789Mean 3.81RMS 3.407Hits per Event - Plane 1N1600h_hit1Entries 3919Mean 3.241RMS 3.05180014001200600100040080060020040020000 2 4 6 8 10 12 14 16 18 20N hit00 2 4 6 8 10 12 14 16 18 20N hitFigure 5.13: Number of hits per event for both 2D planes. Events with no hits werecut from the data. On can clearly identify a peak at four hits per event, which isexpected from the layout of the detector. However, the distribution shows also eventswith more than ten hits. These are caused mainly by noise or multiple muon events.Hitmap after noise cut - Plane 0N hits908070605040302010h_hitmapc0Entries 5794Mean 46.26RMS 27.6500 10 20 30 40 50 60 70 80 90TubeHitmap after noise cut - Plane 1N hits24022020018016014012010080604020h_hitmapc1Entries 7850Mean 38.1RMS 25.5700 10 20 30 40 50 60 70 80 90TubeFigure 5.14: Hit map of all tubes in the CMT. The peaks in the x − z-plane (plane1) can be explained by the poor trigger efficiency of trigger scintillators A and B.Therefore a cut of n hits > 0 is applied for each 2D plane.The number of hits per event is shown in Fig. 5.13. As expected, a peak atn hit = 4 is observed. However, the distributions show a rather long tail towardslarger values. A large number of hits can occur when a track with a steep inclinationcrosses the detector. However, this cannot explain the extent of the tail in thedistribution. By looking at single events, one finds that many of the events inquestion show fake hits probably occurring from cross talk and also δ electrons. Asecond cause for large values of n hit are multiple muon events, where there is anexpected average of eight hits per event (see also Fig.5.17).Fig. 5.14 shows the hit maps for both 2D planes. All tubes except tube 0 inmodule 1.0 seem to be working fine. However, instead of a homogeneous distribution,four distinct peaks can be seen for the same module. These are a hint for a systematicerror in the setup. The error source could be identified in a poor efficiency in someof the trigger scintillators, namely scintillators A and B (cf. Fig. 5.1). Due the thesegmentation of the trigger plane, the characteristic shapes occur. The (presumablywell working) trigger scintillators C and D are the small ones on the left facingthe x − z-plane. Hence, tubes located at small x show significantly more hits (cf.Fig. C.1 for a channel map of each tube). The peak maximum reduces slightlyfor each layer of tubes the further they are away from the scintillator, but it also81