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

76 3. The Double Chooz experiment
tel-00821629, version 1 - 11 May 2013
Eq. 3.14, convert the response of any energy deposition in PE to its equivalent
at the detector center (⇢=0,z=0). Detector response map obtained at
H capture gamma line is shown in Fig. 3.25. The map is obtained from a
sample of spallation neutron (after muon interacting in the detector) and
neutrinos, respectively for data and MC.
Systematic uncertainties are estimated from the data/MC discrepancy of
the map obtained at Gd-capture line. Like the map used for the energy reconstruction,
Gd-capture response map is obtained from spallation-neutrons
and neutrinos, respectively for data and MC. The relative di↵erence across
the Target volume is measured to be 0.43 %.
The response stability factor, f stability of Eq. 3.14, take into account variation
of the detector response due to drift arising from variations in readout
gain and variation of number of channels used to compute the total
deposited charge. Relative variation of the detector response is shown in
Fig. 3.26. Systematic uncertainties from remaining instability are estimated
to be 0.61 % from the relative stability of the H-capture peak, obtained from
spallation neutron over the entire data taking [42].
Figure 3.26: Stability of the reconstructed energy as obtained from the spallation
neutron H-capture peak, over the entire data taking. The observed
steps correspond to power-cycle periods.
Finally the last stage of calibration provide the absolute MeV scale to both
data and MC. The MeV scale is defined by the position of the 2.2 MeVn-H
capture peak. Conversion factor of about 230 PE/MeV is obtained using
neutron from 252 Cf calibration source deployed in the center of the detector.
The conversion factor is measured both for data and MC as shown in
Fig. 3.27. The MeV calibration was measured on 18th August 2011 when
the 252 Cf was deployed. This moment in time is defined as t 0 reference time
for the stability calibration since the response changes before and after.
Some data/MC discrepancies in the absolute energy scale can arise from
the relative non-linearity across the prompt energy spectrum range, since