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

150 5. Correlated background
is then expected to be equivalent to the spectrum one would obtain selecting
the delayed events at low energy, in [6, 12] MeV.
In order to validate such assumption, the prompt spectrum obtained selecting
the delayed event at high energy is compared to the one obtained from
a new SM selection, performed by requiring the delayed candidates at low
energy. A contamination from ¯⌫ e and FN is expected since the delayed neutrons
from these events are selected in the same energy window. In order
to reduce such contaminations, the prompt energy is selected > 15 MeV,
to minimise the ¯⌫ e contamination, and the correlation time between the
prompt and the delayed candidate is set to [2, 4] µs ,tominimisetheFN
contamination. The SM selection cuts for both low and high delayed energy
are summarised in Tab. 5.16.
tel-00821629, version 1 - 11 May 2013
Entries/(2 MeV)
Selection Prompt Delayed T
MeV MeV µs
High delayed energy [0.5, 60] [20, 60] [2, 4]
Low delayed energy [15, 30] [6, 12] [2, 4]
Table 5.16: High and low delayed energy selection cut.
Delayed energy
Entries/(0.25 MeV)
12
10
8
0.7
0.6
0.5
Ed [20, 60] MeV
Ed [6; 12] MeV
6
4
2
0.4
0.3
0.2
0.1
0
0 2 10 4 20 630 840 10 50 12 60
Prompt
prompt
energy Energy E
(MeV)
(MeV)
Figure 5.30: Comparison between SM prompt spectrum obtained by selecting
the delayed candidate at high energy, [20, 60] MeV, and low energy,
[6, 12] MeV. The prompt spectra are in agreement within uncertainty.