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Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Experimentelle Elementarteilchenphysik

Michael Unger (1999)

Detection of cosmic muons with scintillating tiles on top of the L3 detector

Diplom Thesis, Humboldt Universität zu Berlin.

Since 1998 the L3+Cosmics experiment is measuring the momenta of cosmic
muons with the muon-spectrometer of the L3 detector. The main physics
goal is the determination of the absolute muon ux as a function of the mo-
mentum between 20 and 2000 GeV. For the determination of the arrival time
t0 of the muons, which is needed for the reconstruction of the tracks, a large
scintillator array of 72 m2 has been installed on top of the detector. It con-
sists of twelve modules, each of them is read out by two photo multipliers in
This thesis describes the monitoring of the scintillators and the determina-
tion of their e ciencies.
A program has been developed to control the read out system of the photo-
multipliers and to monitor their coincidence rates.
For a certain kind of muon tracks, it is possible to determine their arrival
time independently from the time measurement in the scintillators with an
accuracy of t0 = 5:2 0:1ns. Those events were used to determine the
e ciency of the di erent scintillator modules. Their mean e ciency is
                    " = 0:933 0:003(stat:) 0:005(sys:) :