Etude de bruit de fond induit par les muons dans l'expérience ...

tel-00724955, version 1 - 23 Aug 2012
4.5 Tracking muon candidates 89
side orientation 〈Esimu〉 (MeV) ELMPV (ADC-ch)
upper level Top horizontal 11.8 686.8
North vertical (ss) 20.8 (1.8) 1254.3 (1.8)
South vertical (ss) 20.7 (1.7) 1269.0 (1.8)
NEMO vertical (ls) 23.7 (2.9) 1565.5 (2.3)
East vertical (ls) 24.0 (2.0) 1887.3 (2.7)
lower level East vertical (ls) 23.8 (2.0) 1984.7 (2.8)
South vertical (ls) 19.6 (1.7) 1914.0 (2.8)
North vertical (ls) 19.9 (1.7) 1719.8 (2.5)
NEMO vertical (ls) 23.9 (2.0) 1670.7 (2.4)
Bottom horizontal 12.2 (1.0) 1263.2 (1.8)
Table 4.2: Mean muon energy deposit (simulation and experimental) in plastic
scintillator modules for different orientation in the EDELWEISS-II setup. Vertical
modules are laid out either on the short side (ss) or on the long side (ls). In brackets
are the relative contribution of a side compare to the Top one. The muon generation
is from [184]. The measured LPMV is for muon candidates of a side of a level, which
are in coincidence with the other level. This comparison works only if all modules
are perfectly calibrated to the same gain, which is not the case.
on their length (4 m , 3.75 m, 3.15 m and 2 m) rather than individually to increase
the statistics. The resulting spectrum of the time difference coming from both ends
of a module is shown per set in Figure 4.5. Each end of a spectrum can be fit by
a Gaussian function. The size of the module is set to correspond to the number of
channels between the two Gaussian fits at mid-height:
4 m module ≡ 76 TDC-ch (4.6)
3.75 m module ≡ 68 TDC-ch (4.7)
3.15 m module ≡ 60 TDC-ch (4.8)
2 m module ≡ 36 TDC-ch (4.9)
The spatial resolution of a module is defined looking at the time difference of
coincidences between a module n and its neighbor n + 1 of one level and further
in coincidence with the other level of the veto system. Three sets of modules are
now defined depending on their position: Top modules, vertical modules along their
shorter side (North and South of the upper level), and vertical modules along their
longer side (North and South of the lower level, and East and NEMO). The biplot
of the time difference within the neighboring module n+1 versus the time difference
within module n is shown per set in Figure 4.6. The width of this biplot distribution
is the spatial resolution of a type of modules. The projection of the biplot can be fit
by a Gaussian with a width of 2σ. The resolutions obtained are in TDC channels:
σtop = 10.20 TDC-ch (4.10)
σss = 10.33 TDC-ch (4.11)
σls = 6.53 TDC-ch (4.12)
The sets defined per size are associated to the sets defined per position. The 4 m
module are modules from the Top side and the North and South lower sides, they
have a resolution σtop. The 3.15 m modules are the vertical modules along their
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