Etude et impact du bruit de fond corrélé pour la mesure de l'angle ...

3.8 Data reconstruction 73
tel-00821629, version 1 - 11 May 2013
Figure 3.23: Scintillator time response obtained from the PMT pulse start
time, corrected by the time of flight of the light between the interaction
vertex and the PMT itself.
via neutron captures or via proton recoils).
The IV detector was designed to tag through going muons with very high
e ciency. The IV was configured to be self-triggered at around ⇠ 10 MeV
equivalent energy deposition, at the inflection point of the IV energy spectrum
in between the natural radioactivity dominated region and the muon
dominated region. Through going cosmic muons are expected to be unmissable
since ⇠ 100 MeV (i.e., roughly 49 cm ⇥ 2 MeV/cm for a MIP-µ) of
deposited energy is expected. The IV-detector based tagging is set as low
as possible around self-triggered energy threshold, Q IV = 10 4 DUQ (i.e.,
roughly 4 ⇥ 1 MeV, which is 4 ⇥ 2174 DUQ = 8588 DUQ as obtained by
an approximate IV energy calibration using through-going muons). This
cut is expected to tag mainly through going muons (IV or both ID and IV)
and fast neutron (via proton recoil in the IV). Dedicated studies performed
within the collaboration demonstrate that the IV e ciency, monotonically
increasing with the energy deposited in the IV, is > 99.999 % at 10 4 DUQ.
Therefore, the only place where muons can sneak into the ID undetected by
the IV is via the chimney. There the ID can be used to tagged those events.
The tagging based on the ID allows to identify the Michel electron from
muon entering through the chimney and stopping on the top of the ID,
therefore not crossing the IV. If the muon did not stop, it would be tagged