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

3.1 The Double Chooz detector 49
tel-00821629, version 1 - 11 May 2013
3.1.6 Outer Veto
Figure 3.6: View of the Outer Veto.
A further improvement with respect to the CHOOZ experiment is the OV.
It is installed above the stainless steel shield, with the purpose to tag muons,
which could cause ¯⌫ e background events through muon correlated physics.
The OV allows to track (x, y) coordinates for muons passing through an
area of 13 m ⇥ 7 m centred on the detector chimney. A smaller upper OV
installed above the chimney allows to cover an area of 1.1 m⇥ 0.30 m left
open around the chimney.
The OV consists of 64 plastic scintillator strips of 5 ⇥ 1 ⇥ 320 cm or 360 cm
coupled to 1.5 mm diameter wavelength shifting optic fibers. The strips are
superimposed to form x and y plane of 32 strips each.
To be noticed that the OV dimensions extend beyond the IV diameter to
allow the tagging of near-by muons not entering in the detector, which could
cause muon correlated physics in the ID.
The OV has been active for about 69 % of the data considered in this work,
while the upper OV has been installed recently and is not considered here.