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

N/dayTime Distribution of BX CMT Flagged events (3 ≤nhit ≤12)98htimeeventEntries 582Mean 1.273e+09RMS 5.483e+067654321031/01 02/03 01/04 01/05 31/05 30/06 30/07 29/08DateFigure 5.18: Time distribution of common events in Borexino and the CMT. Atriggered signal is considered an event, if three or more, but no more than twelve tubeshave been hit in each plane. The gaps in the distribution come from periods wherethe CMT did not take data.5.3 Common Events with BorexinoDespite the poor trigger efficiency of roughly 50%, some tracks passing both theCMT and Borexino could be reconstructed.Due to the trigger setup, events are also recorded when the track does not crossthe CMT detector or passes only an insufficient number of tubes. To get a firstestimate of which occurrences can be considered true events, the basic following cutis applied: In each 2D plane, at least three hits have to be recorded. Also, themaximum number of hits must not exceed twelve. The latter cut is mainly used toreduce noise events from the data. Fig. 5.18 shows the distribution of coincidenceevents over time. It can easily be seen that due to the malfunctioning trigger thedaily number of events is well below the expected value of ∼ 9.6 events per dayfrom the simulation. Altogether, there are 582 events qualifying for reconstruction.However, the basic event selection based on the number of hits also includes certainnoise patterns so that in the end only 392 events could be reconstructed. Usingthese events, a first analysis of the Borexino muon tracking was performed.5.3.1 Borexino Data MatchingBorexino and CMT data are matched on an event by event basis using the timestampof each event. As mentioned before, the CMT trigger signal is also sent to theBorexino DAQ, where a flag is set in case of a common event. From the Borexinodata, all events with a CMT flag are selected. For each event, timestamp, runnumber and event number are extracted into a text file.The raw CMT data is converted to aROOT file for each run. An iteration over both85