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

140 5. Correlated background
Prompt energy
Entries/(1 MeV)
10 2
10
Stop Muon candidates
Off Time coincidence
Delayed energy
Entries/(2 MeV)
10
1
10 -1
1
tel-00821629, version 1 - 11 May 2013
Entries/2"s
0 5 10 15 20 25 30
Energy (MeV)
70
60
50
40
30
20
10
Entries 1690
2
/ ndf
41.44 / 48
Prob 0.7369
p0 33.64 !
0.83
1000 1020 1040 1060 1080 1100
T ("s)
20 25 30 35 40 45 50 55 60
Energy (MeV)
Time difference Time difference
Entries 235
Entries/2"s
80
70
60
50
40
2
/ ndf
4.514 / 1
Prob 0.03362
Const 41.02 !
1.38
Norm 222.1
!
29.5
"
1.908 !
0.182
2 3 4 5 6 7 8 9 10
T ("s)
Figure 5.21: Comparison between SM candidates (black histograms) and
HELN sample obtained by performing o↵-time selection (violet points). The
low energy part of the prompt spectrum (top left) shows the characteristic
shape of natural radioactivity gamma and is well reproduced by the o↵-time
sample. O↵-time coincidence with higher energy prompt candidate are also
observed. The delayed energy spectrum (top right) shows less HELN contamination
in the low energy part of delayed spectrum, < 40 MeV, while
the o↵-time selection reproduce well the higher part of the spectrum, suggesting
more contamination. The prompt delayed time distribution shows
a flat distribution for the o↵-time selection (bottom left) while the on-time
sample (bottom right) shows the correlated distribution from SM, with a
time constant of 1.9 ± 0.2 µs.